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 $188.75   3.303%   $194.9844   $194.98   $195.00   $195.00  
  Purchase #2 $62.91   13.764%   $71.5689   $71.57   $71.55   $71.60  
  Purchase #3 $155.83   8.575%   $169.1924   $169.19   $169.20   $169.20  
  Purchase #4 $61.95   6.789%   $66.1558   $66.16   $66.15   $66.20  
  Purchase #5 $230.48   3.519%   $238.5906   $238.59   $238.60   $238.60  
  Purchase #6 $161.63   11.263%   $179.8344   $179.83   $179.85   $179.80  
  Purchase #7 $122.33   13.290%   $138.5877   $138.59   $138.60   $138.60  
  7 purchase totals = $983.88       $1,058.9142   $1,058.91   $1,058.95   $1,059.00