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 $195.97   7.729%   $211.1165   $211.12   $211.10   $211.10  
  Purchase #2 $189.78   3.810%   $197.0106   $197.01   $197.00   $197.00  
  Purchase #3 $62.99   4.123%   $65.5871   $65.59   $65.60   $65.60  
  Purchase #4 $186.77   11.208%   $207.7032   $207.70   $207.70   $207.70  
  Purchase #5 $184.49   10.114%   $203.1493   $203.15   $203.15   $203.10  
  Purchase #6 $210.63   6.769%   $224.8875   $224.89   $224.90   $224.90  
  Purchase #7 $237.54   9.153%   $259.282   $259.28   $259.30   $259.30  
  7 purchase totals = $1,268.17       $1,368.7362   $1,368.74   $1,368.75   $1,368.70