Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $195.65   7.827%   $210.9635   $210.96   $210.95   $211.00  
  Purchase #2 $191.77   10.382%   $211.6796   $211.68   $211.70   $211.70  
  Purchase #3 $246.83   8.583%   $268.0154   $268.02   $268.00   $268.00  
  Purchase #4 $147.34   12.180%   $165.286   $165.29   $165.30   $165.30  
  Purchase #5 $172.82   10.517%   $190.9955   $191.00   $191.00   $191.00  
  Purchase #6 $139.97   8.324%   $151.6211   $151.62   $151.60   $151.60  
  Purchase #7 $168.74   11.350%   $187.892   $187.89   $187.90   $187.90  
  7 purchase totals = $1,263.12       $1,386.4531   $1,386.46   $1,386.45   $1,386.50