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 $216.31   9.546%   $236.959   $236.96   $236.95   $237.00  
  Purchase #2 $98.75   11.148%   $109.7587   $109.76   $109.75   $109.80  
  Purchase #3 $17.95   11.120%   $19.946   $19.95   $19.95   $19.90  
  Purchase #4 $167.60   12.504%   $188.5567   $188.56   $188.55   $188.60  
  Purchase #5 $29.45   6.213%   $31.2797   $31.28   $31.30   $31.30  
  Purchase #6 $235.90   7.514%   $253.6255   $253.63   $253.65   $253.60  
  Purchase #7 $165.90   11.530%   $185.0283   $185.03   $185.05   $185.00  
  7 purchase totals = $931.86       $1,025.1539   $1,025.17   $1,025.20   $1,025.20