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 $85.80   9.164%   $93.6627   $93.66   $93.65   $93.70  
  Purchase #2 $98.56   10.495%   $108.9039   $108.90   $108.90   $108.90  
  Purchase #3 $150.43   7.478%   $161.6792   $161.68   $161.70   $161.70  
  Purchase #4 $184.33   7.851%   $198.8017   $198.80   $198.80   $198.80  
  Purchase #5 $87.71   10.302%   $96.7459   $96.75   $96.75   $96.70  
  Purchase #6 $177.70   9.859%   $195.2194   $195.22   $195.20   $195.20  
  Purchase #7 $91.56   4.645%   $95.813   $95.81   $95.80   $95.80  
  7 purchase totals = $876.09       $950.8258   $950.82   $950.80   $950.80