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 $46.44   6.820%   $49.6072   $49.61   $49.60   $49.60  
  Purchase #2 $205.52   7.103%   $220.1181   $220.12   $220.10   $220.10  
  Purchase #3 $207.52   3.873%   $215.5572   $215.56   $215.55   $215.60  
  Purchase #4 $22.32   3.674%   $23.14   $23.14   $23.15   $23.10  
  Purchase #5 $93.92   4.315%   $97.9726   $97.97   $97.95   $98.00  
  Purchase #6 $207.31   6.761%   $221.3262   $221.33   $221.35   $221.30  
  Purchase #7 $213.86   5.817%   $226.3002   $226.30   $226.30   $226.30  
  7 purchase totals = $996.89       $1,054.0215   $1,054.03   $1,054.00   $1,054.00