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 $195.76   5.501%   $206.5288   $206.53   $206.55   $206.50  
  Purchase #2 $152.89   8.480%   $165.8551   $165.86   $165.85   $165.90  
  Purchase #3 $55.81   5.128%   $58.6719   $58.67   $58.65   $58.70  
  Purchase #4 $231.41   8.513%   $251.1099   $251.11   $251.10   $251.10  
  Purchase #5 $68.72   8.198%   $74.3537   $74.35   $74.35   $74.40  
  Purchase #6 $127.41   13.261%   $144.3058   $144.31   $144.30   $144.30  
  Purchase #7 $154.26   10.312%   $170.1673   $170.17   $170.15   $170.20  
  7 purchase totals = $986.26       $1,070.9925   $1,071.00   $1,070.95   $1,071.10