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 $46.62   5.669%   $49.2629   $49.26   $49.25   $49.30  
  Purchase #2 $94.52   3.443%   $97.7743   $97.77   $97.75   $97.80  
  Purchase #3 $112.30   3.150%   $115.8375   $115.84   $115.85   $115.80  
  Purchase #4 $220.30   10.618%   $243.6915   $243.69   $243.70   $243.70  
  Purchase #5 $247.99   9.858%   $272.4369   $272.44   $272.45   $272.40  
  Purchase #6 $183.72   5.116%   $193.1191   $193.12   $193.10   $193.10  
  Purchase #7 $203.46   9.771%   $223.3401   $223.34   $223.35   $223.30  
  7 purchase totals = $1,108.91       $1,195.4623   $1,195.46   $1,195.45   $1,195.40