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 $113.84   8.644%   $123.6803   $123.68   $123.70   $123.70  
  Purchase #2 $151.91   10.571%   $167.9684   $167.97   $167.95   $168.00  
  Purchase #3 $178.70   3.755%   $185.4102   $185.41   $185.40   $185.40  
  Purchase #4 $139.68   8.716%   $151.8545   $151.85   $151.85   $151.90  
  Purchase #5 $50.71   9.659%   $55.6081   $55.61   $55.60   $55.60  
  Purchase #6 $175.52   13.269%   $198.8097   $198.81   $198.80   $198.80  
  Purchase #7 $160.91   5.521%   $169.7938   $169.79   $169.80   $169.80  
  7 purchase totals = $971.27       $1,053.1250   $1,053.12   $1,053.10   $1,053.20