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 $68.99   9.297%   $75.404   $75.40   $75.40   $75.40  
  Purchase #2 $209.42   12.375%   $235.3357   $235.34   $235.35   $235.30  
  Purchase #3 $202.97   9.262%   $221.7691   $221.77   $221.75   $221.80  
  Purchase #4 $166.51   5.840%   $176.2342   $176.23   $176.25   $176.20  
  Purchase #5 $191.38   8.600%   $207.8387   $207.84   $207.85   $207.80  
  Purchase #6 $181.92   11.403%   $202.6643   $202.66   $202.65   $202.70  
  Purchase #7 $199.45   3.215%   $205.8623   $205.86   $205.85   $205.90  
  7 purchase totals = $1,220.64       $1,325.1083   $1,325.10   $1,325.10   $1,325.10