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 $62.67   3.776%   $65.0364   $65.04   $65.05   $65.00  
  Purchase #2 $194.49   4.653%   $203.5396   $203.54   $203.55   $203.50  
  Purchase #3 $244.64   12.617%   $275.5062   $275.51   $275.50   $275.50  
  Purchase #4 $234.78   9.427%   $256.9127   $256.91   $256.90   $256.90  
  Purchase #5 $145.75   8.789%   $158.56   $158.56   $158.55   $158.60  
  Purchase #6 $128.96   11.736%   $144.0947   $144.09   $144.10   $144.10  
  Purchase #7 $94.90   3.359%   $98.0877   $98.09   $98.10   $98.10  
  7 purchase totals = $1,106.19       $1,201.7373   $1,201.74   $1,201.75   $1,201.70