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 $184.76   10.192%   $203.5907   $203.59   $203.60   $203.60  
  Purchase #2 $211.49   10.782%   $234.2929   $234.29   $234.30   $234.30  
  Purchase #3 $29.42   10.318%   $32.4556   $32.46   $32.45   $32.50  
  Purchase #4 $169.53   8.371%   $183.7214   $183.72   $183.70   $183.70  
  Purchase #5 $237.48   10.500%   $262.4154   $262.42   $262.40   $262.40  
  Purchase #6 $185.36   5.324%   $195.2286   $195.23   $195.25   $195.20  
  Purchase #7 $98.29   4.751%   $102.9598   $102.96   $102.95   $103.00  
  7 purchase totals = $1,116.33       $1,214.6644   $1,214.67   $1,214.65   $1,214.70