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 $64.79   11.178%   $72.0322   $72.03   $72.05   $72.00  
  Purchase #2 $67.59   9.412%   $73.9516   $73.95   $73.95   $74.00  
  Purchase #3 $59.97   5.749%   $63.4177   $63.42   $63.40   $63.40  
  Purchase #4 $152.82   5.846%   $161.7539   $161.75   $161.75   $161.80  
  Purchase #5 $176.45   11.254%   $196.3077   $196.31   $196.30   $196.30  
  Purchase #6 $14.29   3.767%   $14.8283   $14.83   $14.85   $14.80  
  Purchase #7 $166.77   5.754%   $176.3659   $176.37   $176.35   $176.40  
  7 purchase totals = $702.68       $758.6573   $758.66   $758.65   $758.70