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 $182.40   6.796%   $194.7959   $194.80   $194.80   $194.80  
  Purchase #2 $137.41   5.276%   $144.6598   $144.66   $144.65   $144.70  
  Purchase #3 $168.83   10.772%   $187.0164   $187.02   $187.00   $187.00  
  Purchase #4 $21.75   12.673%   $24.5064   $24.51   $24.50   $24.50  
  Purchase #5 $138.79   7.681%   $149.4505   $149.45   $149.45   $149.50  
  Purchase #6 $244.43   13.594%   $277.6578   $277.66   $277.65   $277.70  
  Purchase #7 $50.96   6.526%   $54.2856   $54.29   $54.30   $54.30  
  7 purchase totals = $944.57       $1,032.3724   $1,032.39   $1,032.35   $1,032.50