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 $163.50   7.312%   $175.4551   $175.46   $175.45   $175.50  
  Purchase #2 $37.79   8.814%   $41.1208   $41.12   $41.10   $41.10  
  Purchase #3 $149.51   8.293%   $161.9089   $161.91   $161.90   $161.90  
  Purchase #4 $141.60   11.411%   $157.758   $157.76   $157.75   $157.80  
  Purchase #5 $52.73   10.658%   $58.35   $58.35   $58.35   $58.40  
  Purchase #6 $179.48   7.843%   $193.5566   $193.56   $193.55   $193.60  
  Purchase #7 $228.96   7.427%   $245.9649   $245.96   $245.95   $246.00  
  7 purchase totals = $953.57       $1,034.1143   $1,034.12   $1,034.05   $1,034.30