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 $176.93   9.674%   $194.0462   $194.05   $194.05   $194.00  
  Purchase #2 $67.54   13.135%   $76.4114   $76.41   $76.40   $76.40  
  Purchase #3 $151.77   11.221%   $168.8001   $168.80   $168.80   $168.80  
  Purchase #4 $105.58   11.570%   $117.7956   $117.80   $117.80   $117.80  
  Purchase #5 $75.35   4.800%   $78.9668   $78.97   $78.95   $79.00  
  Purchase #6 $216.82   11.404%   $241.5462   $241.55   $241.55   $241.50  
  Purchase #7 $81.39   7.513%   $87.5048   $87.50   $87.50   $87.50  
  7 purchase totals = $875.38       $965.0711   $965.08   $965.05   $965.00