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 $62.26   13.254%   $70.5119   $70.51   $70.50   $70.50  
  Purchase #2 $137.36   5.174%   $144.467   $144.47   $144.45   $144.50  
  Purchase #3 $194.95   3.759%   $202.2782   $202.28   $202.30   $202.30  
  Purchase #4 $199.70   5.676%   $211.035   $211.04   $211.05   $211.00  
  Purchase #5 $218.72   7.427%   $234.9643   $234.96   $234.95   $235.00  
  Purchase #6 $48.90   10.473%   $54.0213   $54.02   $54.00   $54.00  
  Purchase #7 $169.77   4.486%   $177.3859   $177.39   $177.40   $177.40  
  7 purchase totals = $1,031.66       $1,094.6636   $1,094.67   $1,094.65   $1,094.70