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 $84.36   10.480%   $93.2009   $93.20   $93.20   $93.20  
  Purchase #2 $101.68   8.362%   $110.1825   $110.18   $110.20   $110.20  
  Purchase #3 $161.38   4.855%   $169.215   $169.22   $169.20   $169.20  
  Purchase #4 $221.32   9.601%   $242.5689   $242.57   $242.55   $242.60  
  Purchase #5 $150.39   13.843%   $171.2085   $171.21   $171.20   $171.20  
  Purchase #6 $142.62   3.684%   $147.8741   $147.87   $147.85   $147.90  
  Purchase #7 $155.63   13.679%   $176.9186   $176.92   $176.90   $176.90  
  7 purchase totals = $1,017.38       $1,111.1685   $1,111.17   $1,111.10   $1,111.20