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 $216.42   3.237%   $223.4255   $223.43   $223.45   $223.40  
  Purchase #2 $13.64   4.424%   $14.2434   $14.24   $14.25   $14.20  
  Purchase #3 $157.69   11.696%   $176.1334   $176.13   $176.15   $176.10  
  Purchase #4 $54.60   8.558%   $59.2727   $59.27   $59.25   $59.30  
  Purchase #5 $165.95   12.483%   $186.6655   $186.67   $186.65   $186.70  
  Purchase #6 $132.50   5.689%   $140.0379   $140.04   $140.05   $140.00  
  Purchase #7 $202.65   11.145%   $225.2353   $225.24   $225.25   $225.20  
  7 purchase totals = $943.45       $1,025.0137   $1,025.02   $1,025.05   $1,024.90