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 $82.96   11.677%   $92.6472   $92.65   $92.65   $92.60  
  Purchase #2 $232.41   6.391%   $247.2633   $247.26   $247.25   $247.30  
  Purchase #3 $150.64   10.448%   $166.3789   $166.38   $166.40   $166.40  
  Purchase #4 $183.93   12.606%   $207.1162   $207.12   $207.10   $207.10  
  Purchase #5 $221.35   5.196%   $232.8513   $232.85   $232.85   $232.90  
  Purchase #6 $17.32   7.629%   $18.6413   $18.64   $18.65   $18.60  
  Purchase #7 $238.49   10.404%   $263.3025   $263.30   $263.30   $263.30  
  7 purchase totals = $1,127.10       $1,228.2007   $1,228.20   $1,228.20   $1,228.20