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 $76.97   13.231%   $87.1539   $87.15   $87.15   $87.20  
  Purchase #2 $174.73   11.810%   $195.3656   $195.37   $195.35   $195.40  
  Purchase #3 $23.51   8.226%   $25.4439   $25.44   $25.45   $25.40  
  Purchase #4 $89.76   5.865%   $95.0244   $95.02   $95.00   $95.00  
  Purchase #5 $190.45   5.745%   $201.3914   $201.39   $201.40   $201.40  
  Purchase #6 $212.43   7.246%   $227.8227   $227.82   $227.80   $227.80  
  Purchase #7 $179.64   12.406%   $201.9261   $201.93   $201.95   $201.90  
  7 purchase totals = $947.49       $1,034.1280   $1,034.12   $1,034.10   $1,034.10