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 $222.85   8.570%   $241.9482   $241.95   $241.95   $241.90  
  Purchase #2 $193.34   6.171%   $205.271   $205.27   $205.25   $205.30  
  Purchase #3 $119.89   8.317%   $129.8613   $129.86   $129.85   $129.90  
  Purchase #4 $94.85   7.527%   $101.9894   $101.99   $102.00   $102.00  
  Purchase #5 $248.98   4.642%   $260.5377   $260.54   $260.55   $260.50  
  Purchase #6 $167.60   9.874%   $184.1488   $184.15   $184.15   $184.10  
  Purchase #7 $41.34   12.799%   $46.6311   $46.63   $46.65   $46.60  
  7 purchase totals = $1,088.85       $1,170.3875   $1,170.39   $1,170.40   $1,170.30