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 $92.58   3.446%   $95.7703   $95.77   $95.75   $95.80  
  Purchase #2 $238.28   11.331%   $265.2795   $265.28   $265.30   $265.30  
  Purchase #3 $37.97   12.145%   $42.5815   $42.58   $42.60   $42.60  
  Purchase #4 $202.43   6.520%   $215.6284   $215.63   $215.65   $215.60  
  Purchase #5 $40.45   11.426%   $45.0718   $45.07   $45.05   $45.10  
  Purchase #6 $174.67   11.196%   $194.2261   $194.23   $194.25   $194.20  
  Purchase #7 $87.65   7.169%   $93.9336   $93.93   $93.95   $93.90  
  7 purchase totals = $874.03       $952.4912   $952.49   $952.55   $952.50