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 $58.39   6.128%   $61.9681   $61.97   $61.95   $62.00  
  Purchase #2 $219.40   11.571%   $244.7868   $244.79   $244.80   $244.80  
  Purchase #3 $72.26   11.534%   $80.5945   $80.59   $80.60   $80.60  
  Purchase #4 $215.44   4.193%   $224.4734   $224.47   $224.45   $224.50  
  Purchase #5 $112.90   5.264%   $118.8431   $118.84   $118.85   $118.80  
  Purchase #6 $170.34   5.802%   $180.2231   $180.22   $180.20   $180.20  
  Purchase #7 $237.32   10.607%   $262.4925   $262.49   $262.50   $262.50  
  7 purchase totals = $1,086.05       $1,173.3815   $1,173.37   $1,173.35   $1,173.40