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 $32.52   6.847%   $34.7466   $34.75   $34.75   $34.70  
  Purchase #2 $206.37   9.333%   $225.6305   $225.63   $225.65   $225.60  
  Purchase #3 $247.29   3.313%   $255.4827   $255.48   $255.50   $255.50  
  Purchase #4 $117.29   4.664%   $122.7604   $122.76   $122.75   $122.80  
  Purchase #5 $243.86   3.814%   $253.1608   $253.16   $253.15   $253.20  
  Purchase #6 $61.62   8.329%   $66.7523   $66.75   $66.75   $66.80  
  Purchase #7 $158.33   8.492%   $171.7754   $171.78   $171.80   $171.80  
  7 purchase totals = $1,067.28       $1,130.3087   $1,130.31   $1,130.35   $1,130.40