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 $88.57   9.733%   $97.1905   $97.19   $97.20   $97.20  
  Purchase #2 $213.96   8.583%   $232.3242   $232.32   $232.30   $232.30  
  Purchase #3 $219.51   13.112%   $248.2922   $248.29   $248.30   $248.30  
  Purchase #4 $52.60   3.748%   $54.5714   $54.57   $54.55   $54.60  
  Purchase #5 $216.37   5.551%   $228.3807   $228.38   $228.40   $228.40  
  Purchase #6 $186.27   9.718%   $204.3717   $204.37   $204.35   $204.40  
  Purchase #7 $213.50   11.571%   $238.2041   $238.20   $238.20   $238.20  
  7 purchase totals = $1,190.78       $1,303.3348   $1,303.32   $1,303.30   $1,303.40