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 $89.64   6.212%   $95.2084   $95.21   $95.20   $95.20  
  Purchase #2 $236.85   7.784%   $255.2864   $255.29   $255.30   $255.30  
  Purchase #3 $124.75   4.345%   $130.1704   $130.17   $130.15   $130.20  
  Purchase #4 $185.91   9.408%   $203.4004   $203.40   $203.40   $203.40  
  Purchase #5 $68.85   3.804%   $71.4691   $71.47   $71.45   $71.50  
  Purchase #6 $223.85   12.133%   $251.0097   $251.01   $251.00   $251.00  
  Purchase #7 $187.46   11.780%   $209.5428   $209.54   $209.55   $209.50  
  7 purchase totals = $1,117.31       $1,216.0872   $1,216.09   $1,216.05   $1,216.10