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 $186.87   4.172%   $194.6662   $194.67   $194.65   $194.70  
  Purchase #2 $60.39   4.812%   $63.296   $63.30   $63.30   $63.30  
  Purchase #3 $178.69   13.429%   $202.6863   $202.69   $202.70   $202.70  
  Purchase #4 $40.98   10.634%   $45.3378   $45.34   $45.35   $45.30  
  Purchase #5 $33.79   7.720%   $36.3986   $36.40   $36.40   $36.40  
  Purchase #6 $246.25   12.763%   $277.6789   $277.68   $277.70   $277.70  
  Purchase #7 $189.86   11.415%   $211.5325   $211.53   $211.55   $211.50  
  7 purchase totals = $936.83       $1,031.5963   $1,031.61   $1,031.65   $1,031.60