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 $160.26   11.765%   $179.1146   $179.11   $179.10   $179.10  
  Purchase #2 $54.54   11.756%   $60.9517   $60.95   $60.95   $61.00  
  Purchase #3 $28.26   3.678%   $29.2994   $29.30   $29.30   $29.30  
  Purchase #4 $192.73   4.767%   $201.9174   $201.92   $201.90   $201.90  
  Purchase #5 $101.75   5.711%   $107.5609   $107.56   $107.55   $107.60  
  Purchase #6 $156.29   4.610%   $163.495   $163.50   $163.50   $163.50  
  Purchase #7 $202.67   10.446%   $223.8409   $223.84   $223.85   $223.80  
  7 purchase totals = $896.50       $966.1799   $966.18   $966.15   $966.20