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 $68.75   10.530%   $75.9894   $75.99   $76.00   $76.00  
  Purchase #2 $213.46   4.861%   $223.8363   $223.84   $223.85   $223.80  
  Purchase #3 $177.65   9.516%   $194.5552   $194.56   $194.55   $194.60  
  Purchase #4 $44.39   10.763%   $49.1677   $49.17   $49.15   $49.20  
  Purchase #5 $205.33   6.735%   $219.159   $219.16   $219.15   $219.20  
  Purchase #6 $232.40   6.711%   $247.9964   $248.00   $248.00   $248.00  
  Purchase #7 $245.92   7.800%   $265.1018   $265.10   $265.10   $265.10  
  7 purchase totals = $1,187.90       $1,275.8058   $1,275.82   $1,275.80   $1,275.90