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 $173.77   12.582%   $195.6337   $195.63   $195.65   $195.60  
  Purchase #2 $222.27   8.618%   $241.4252   $241.43   $241.45   $241.40  
  Purchase #3 $238.63   12.299%   $267.9791   $267.98   $268.00   $268.00  
  Purchase #4 $20.45   8.797%   $22.249   $22.25   $22.25   $22.20  
  Purchase #5 $160.89   7.121%   $172.347   $172.35   $172.35   $172.30  
  Purchase #6 $17.86   6.512%   $19.023   $19.02   $19.00   $19.00  
  Purchase #7 $142.39   3.638%   $147.5701   $147.57   $147.55   $147.60  
  7 purchase totals = $976.26       $1,066.2271   $1,066.23   $1,066.25   $1,066.10