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 $43.72   6.630%   $46.6186   $46.62   $46.60   $46.60  
  Purchase #2 $170.34   7.824%   $183.6674   $183.67   $183.65   $183.70  
  Purchase #3 $202.89   5.200%   $213.4403   $213.44   $213.45   $213.40  
  Purchase #4 $219.72   3.362%   $227.107   $227.11   $227.10   $227.10  
  Purchase #5 $46.80   6.515%   $49.849   $49.85   $49.85   $49.80  
  Purchase #6 $106.52   12.168%   $119.4814   $119.48   $119.50   $119.50  
  Purchase #7 $183.92   5.126%   $193.3477   $193.35   $193.35   $193.30  
  7 purchase totals = $973.91       $1,033.5114   $1,033.52   $1,033.50   $1,033.40