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 $55.51   12.168%   $62.2645   $62.26   $62.25   $62.30  
  Purchase #2 $167.65   3.301%   $173.1841   $173.18   $173.20   $173.20  
  Purchase #3 $235.98   6.405%   $251.0945   $251.09   $251.10   $251.10  
  Purchase #4 $246.47   5.808%   $260.785   $260.79   $260.80   $260.80  
  Purchase #5 $95.41   7.248%   $102.3253   $102.33   $102.35   $102.30  
  Purchase #6 $103.54   4.123%   $107.809   $107.81   $107.80   $107.80  
  Purchase #7 $120.76   5.532%   $127.4404   $127.44   $127.45   $127.40  
  7 purchase totals = $1,025.32       $1,084.9028   $1,084.90   $1,084.95   $1,084.90