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 $52.67   9.351%   $57.5952   $57.60   $57.60   $57.60  
  Purchase #2 $96.63   13.345%   $109.5253   $109.53   $109.55   $109.50  
  Purchase #3 $213.38   9.566%   $233.7919   $233.79   $233.80   $233.80  
  Purchase #4 $70.58   12.689%   $79.5359   $79.54   $79.55   $79.50  
  Purchase #5 $145.84   4.657%   $152.6318   $152.63   $152.65   $152.60  
  Purchase #6 $43.88   10.351%   $48.422   $48.42   $48.40   $48.40  
  Purchase #7 $108.36   5.201%   $113.9958   $114.00   $114.00   $114.00  
  7 purchase totals = $731.34       $795.4979   $795.51   $795.55   $795.40