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 $56.43   10.381%   $62.288   $62.29   $62.30   $62.30  
  Purchase #2 $179.83   6.842%   $192.134   $192.13   $192.15   $192.10  
  Purchase #3 $241.97   3.842%   $251.2665   $251.27   $251.25   $251.30  
  Purchase #4 $243.80   11.294%   $271.3348   $271.33   $271.35   $271.30  
  Purchase #5 $40.84   10.436%   $45.1021   $45.10   $45.10   $45.10  
  Purchase #6 $154.87   9.829%   $170.0922   $170.09   $170.10   $170.10  
  Purchase #7 $63.47   7.844%   $68.4486   $68.45   $68.45   $68.40  
  7 purchase totals = $981.21       $1,060.6662   $1,060.66   $1,060.70   $1,060.60