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 $58.29   3.169%   $60.1372   $60.14   $60.15   $60.10  
  Purchase #2 $181.86   13.640%   $206.6657   $206.67   $206.65   $206.70  
  Purchase #3 $178.40   11.722%   $199.312   $199.31   $199.30   $199.30  
  Purchase #4 $93.96   12.722%   $105.9136   $105.91   $105.90   $105.90  
  Purchase #5 $209.68   9.733%   $230.0882   $230.09   $230.10   $230.10  
  Purchase #6 $19.69   12.429%   $22.1373   $22.14   $22.15   $22.10  
  Purchase #7 $199.70   11.486%   $222.6375   $222.64   $222.65   $222.60  
  7 purchase totals = $941.58       $1,046.8915   $1,046.90   $1,046.90   $1,046.80