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 $91.96   4.275%   $95.8913   $95.89   $95.90   $95.90  
  Purchase #2 $178.54   13.211%   $202.1269   $202.13   $202.15   $202.10  
  Purchase #3 $175.28   5.280%   $184.5348   $184.53   $184.55   $184.50  
  Purchase #4 $168.97   6.408%   $179.7976   $179.80   $179.80   $179.80  
  Purchase #5 $21.70   11.491%   $24.1935   $24.19   $24.20   $24.20  
  Purchase #6 $183.61   9.258%   $200.6086   $200.61   $200.60   $200.60  
  Purchase #7 $95.49   13.216%   $108.11   $108.11   $108.10   $108.10  
  7 purchase totals = $915.55       $995.2627   $995.26   $995.30   $995.20