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 $179.29   8.762%   $194.9994   $195.00   $195.00   $195.00  
  Purchase #2 $99.44   9.835%   $109.2199   $109.22   $109.20   $109.20  
  Purchase #3 $33.92   10.233%   $37.391   $37.39   $37.40   $37.40  
  Purchase #4 $226.98   11.645%   $253.4118   $253.41   $253.40   $253.40  
  Purchase #5 $84.51   11.280%   $94.0427   $94.04   $94.05   $94.00  
  Purchase #6 $180.81   11.330%   $201.2958   $201.30   $201.30   $201.30  
  Purchase #7 $28.27   12.738%   $31.871   $31.87   $31.85   $31.90  
  7 purchase totals = $833.22       $922.2316   $922.23   $922.20   $922.20