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 $58.89   8.235%   $63.7396   $63.74   $63.75   $63.70  
  Purchase #2 $210.53   9.421%   $230.364   $230.36   $230.35   $230.40  
  Purchase #3 $51.94   3.142%   $53.572   $53.57   $53.55   $53.60  
  Purchase #4 $178.91   5.528%   $188.8001   $188.80   $188.80   $188.80  
  Purchase #5 $52.95   11.663%   $59.1256   $59.13   $59.15   $59.10  
  Purchase #6 $219.31   3.486%   $226.9551   $226.96   $226.95   $227.00  
  Purchase #7 $207.62   3.727%   $215.358   $215.36   $215.35   $215.40  
  7 purchase totals = $980.15       $1,037.9144   $1,037.92   $1,037.90   $1,038.00