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 $86.59   7.520%   $93.1016   $93.10   $93.10   $93.10  
  Purchase #2 $237.99   12.736%   $268.3004   $268.30   $268.30   $268.30  
  Purchase #3 $65.41   8.810%   $71.1726   $71.17   $71.15   $71.20  
  Purchase #4 $173.94   13.165%   $196.8392   $196.84   $196.85   $196.80  
  Purchase #5 $124.30   5.145%   $130.6952   $130.70   $130.70   $130.70  
  Purchase #6 $203.89   7.655%   $219.4978   $219.50   $219.50   $219.50  
  Purchase #7 $62.94   8.767%   $68.4579   $68.46   $68.45   $68.50  
  7 purchase totals = $955.06       $1,048.0647   $1,048.07   $1,048.05   $1,048.10