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 $193.92   8.816%   $211.016   $211.02   $211.00   $211.00  
  Purchase #2 $55.61   10.611%   $61.5108   $61.51   $61.50   $61.50  
  Purchase #3 $177.98   7.234%   $190.8551   $190.86   $190.85   $190.90  
  Purchase #4 $107.94   12.429%   $121.3559   $121.36   $121.35   $121.40  
  Purchase #5 $160.72   10.116%   $176.9784   $176.98   $177.00   $177.00  
  Purchase #6 $108.95   6.674%   $116.2213   $116.22   $116.20   $116.20  
  Purchase #7 $242.77   5.562%   $256.2729   $256.27   $256.25   $256.30  
  7 purchase totals = $1,047.89       $1,134.2104   $1,134.22   $1,134.15   $1,134.30