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 $91.94   3.422%   $95.0862   $95.09   $95.10   $95.10  
  Purchase #2 $89.32   5.808%   $94.5077   $94.51   $94.50   $94.50  
  Purchase #3 $162.31   12.498%   $182.5955   $182.60   $182.60   $182.60  
  Purchase #4 $208.54   12.862%   $235.3624   $235.36   $235.35   $235.40  
  Purchase #5 $75.30   10.203%   $82.9829   $82.98   $83.00   $83.00  
  Purchase #6 $142.95   5.219%   $150.4106   $150.41   $150.40   $150.40  
  Purchase #7 $101.30   12.311%   $113.771   $113.77   $113.75   $113.80  
  7 purchase totals = $871.66       $954.7163   $954.72   $954.70   $954.80