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 $84.69   12.428%   $95.2153   $95.22   $95.20   $95.20  
  Purchase #2 $126.85   4.121%   $132.0775   $132.08   $132.10   $132.10  
  Purchase #3 $49.93   4.609%   $52.2313   $52.23   $52.25   $52.20  
  Purchase #4 $151.75   3.244%   $156.6728   $156.67   $156.65   $156.70  
  Purchase #5 $168.84   6.736%   $180.2131   $180.21   $180.20   $180.20  
  Purchase #6 $218.50   3.761%   $226.7178   $226.72   $226.70   $226.70  
  Purchase #7 $134.31   5.860%   $142.1806   $142.18   $142.20   $142.20  
  7 purchase totals = $934.87       $985.3084   $985.31   $985.30   $985.30