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 $84.64   12.474%   $95.198   $95.20   $95.20   $95.20  
  Purchase #2 $170.66   4.218%   $177.8584   $177.86   $177.85   $177.90  
  Purchase #3 $118.91   4.685%   $124.4809   $124.48   $124.50   $124.50  
  Purchase #4 $67.69   9.512%   $74.1287   $74.13   $74.15   $74.10  
  Purchase #5 $105.84   10.302%   $116.7436   $116.74   $116.75   $116.70  
  Purchase #6 $219.40   9.529%   $240.3066   $240.31   $240.30   $240.30  
  Purchase #7 $107.94   10.772%   $119.5673   $119.57   $119.55   $119.60  
  7 purchase totals = $875.08       $948.2835   $948.29   $948.30   $948.30