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 $83.41   13.615%   $94.7663   $94.77   $94.75   $94.80  
  Purchase #2 $61.56   11.674%   $68.7465   $68.75   $68.75   $68.70  
  Purchase #3 $216.83   11.695%   $242.1883   $242.19   $242.20   $242.20  
  Purchase #4 $197.49   3.809%   $205.0124   $205.01   $205.00   $205.00  
  Purchase #5 $107.96   7.414%   $115.9642   $115.96   $115.95   $116.00  
  Purchase #6 $172.68   12.261%   $193.8523   $193.85   $193.85   $193.90  
  Purchase #7 $158.31   4.356%   $165.206   $165.21   $165.20   $165.20  
  7 purchase totals = $998.24       $1,085.7360   $1,085.74   $1,085.70   $1,085.80