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 $58.93   5.715%   $62.2978   $62.30   $62.30   $62.30  
  Purchase #2 $35.35   3.454%   $36.571   $36.57   $36.55   $36.60  
  Purchase #3 $53.34   3.691%   $55.3088   $55.31   $55.30   $55.30  
  Purchase #4 $103.67   11.728%   $115.8284   $115.83   $115.85   $115.80  
  Purchase #5 $141.67   4.361%   $147.8482   $147.85   $147.85   $147.80  
  Purchase #6 $76.92   3.789%   $79.8345   $79.83   $79.85   $79.80  
  Purchase #7 $244.53   6.331%   $260.0112   $260.01   $260.00   $260.00  
  7 purchase totals = $714.41       $757.6999   $757.70   $757.70   $757.60