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 $69.65   9.538%   $76.2932   $76.29   $76.30   $76.30  
  Purchase #2 $116.56   13.527%   $132.3271   $132.33   $132.35   $132.30  
  Purchase #3 $205.55   11.160%   $228.4894   $228.49   $228.50   $228.50  
  Purchase #4 $179.62   6.428%   $191.166   $191.17   $191.15   $191.20  
  Purchase #5 $240.35   3.198%   $248.0364   $248.04   $248.05   $248.00  
  Purchase #6 $148.89   6.547%   $158.6378   $158.64   $158.65   $158.60  
  Purchase #7 $130.65   12.164%   $146.5423   $146.54   $146.55   $146.50  
  7 purchase totals = $1,091.27       $1,181.4922   $1,181.50   $1,181.55   $1,181.40