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 $95.75   6.276%   $101.7593   $101.76   $101.75   $101.80  
  Purchase #2 $108.27   7.455%   $116.3415   $116.34   $116.35   $116.30  
  Purchase #3 $67.82   13.787%   $77.1703   $77.17   $77.15   $77.20  
  Purchase #4 $47.38   7.375%   $50.8743   $50.87   $50.85   $50.90  
  Purchase #5 $206.98   7.572%   $222.6525   $222.65   $222.65   $222.70  
  Purchase #6 $144.75   7.285%   $155.295   $155.30   $155.30   $155.30  
  Purchase #7 $200.70   5.704%   $212.1479   $212.15   $212.15   $212.10  
  7 purchase totals = $871.65       $936.2408   $936.24   $936.20   $936.30