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 $65.47   3.222%   $67.5794   $67.58   $67.60   $67.60  
  Purchase #2 $137.35   12.738%   $154.8456   $154.85   $154.85   $154.80  
  Purchase #3 $172.81   12.847%   $195.0109   $195.01   $195.00   $195.00  
  Purchase #4 $106.62   9.341%   $116.5794   $116.58   $116.60   $116.60  
  Purchase #5 $233.54   4.466%   $243.9699   $243.97   $243.95   $244.00  
  Purchase #6 $161.31   12.268%   $181.0995   $181.10   $181.10   $181.10  
  Purchase #7 $125.31   13.512%   $142.2419   $142.24   $142.25   $142.20  
  7 purchase totals = $1,002.41       $1,101.3266   $1,101.33   $1,101.35   $1,101.30