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 $215.98   5.618%   $228.1138   $228.11   $228.10   $228.10  
  Purchase #2 $180.79   8.822%   $196.7393   $196.74   $196.75   $196.70  
  Purchase #3 $184.91   6.241%   $196.4502   $196.45   $196.45   $196.50  
  Purchase #4 $27.74   6.669%   $29.59   $29.59   $29.60   $29.60  
  Purchase #5 $92.33   11.205%   $102.6756   $102.68   $102.70   $102.70  
  Purchase #6 $25.76   5.519%   $27.1817   $27.18   $27.20   $27.20  
  Purchase #7 $159.60   8.812%   $173.664   $173.66   $173.65   $173.70  
  7 purchase totals = $887.11       $954.4146   $954.41   $954.45   $954.50