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 $216.59   11.635%   $241.7902   $241.79   $241.80   $241.80  
  Purchase #2 $101.65   6.471%   $108.2278   $108.23   $108.25   $108.20  
  Purchase #3 $32.25   6.353%   $34.2988   $34.30   $34.30   $34.30  
  Purchase #4 $187.82   11.663%   $209.7254   $209.73   $209.75   $209.70  
  Purchase #5 $237.35   9.283%   $259.3832   $259.38   $259.40   $259.40  
  Purchase #6 $54.28   8.564%   $58.9285   $58.93   $58.95   $58.90  
  Purchase #7 $204.62   4.660%   $214.1553   $214.16   $214.15   $214.20  
  7 purchase totals = $1,034.56       $1,126.5092   $1,126.52   $1,126.60   $1,126.50