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 $106.51   11.547%   $118.8087   $118.81   $118.80   $118.80  
  Purchase #2 $187.58   4.224%   $195.5034   $195.50   $195.50   $195.50  
  Purchase #3 $227.57   3.361%   $235.2186   $235.22   $235.20   $235.20  
  Purchase #4 $95.84   13.341%   $108.626   $108.63   $108.65   $108.60  
  Purchase #5 $169.35   8.827%   $184.2985   $184.30   $184.30   $184.30  
  Purchase #6 $91.35   4.198%   $95.1849   $95.18   $95.20   $95.20  
  Purchase #7 $77.62   8.273%   $84.0415   $84.04   $84.05   $84.00  
  7 purchase totals = $955.82       $1,021.6816   $1,021.68   $1,021.70   $1,021.60