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 $114.98   3.776%   $119.3216   $119.32   $119.30   $119.30  
  Purchase #2 $176.29   5.537%   $186.0512   $186.05   $186.05   $186.10  
  Purchase #3 $189.37   5.698%   $200.1603   $200.16   $200.15   $200.20  
  Purchase #4 $23.73   12.657%   $26.7335   $26.73   $26.75   $26.70  
  Purchase #5 $148.72   9.637%   $163.0521   $163.05   $163.05   $163.10  
  Purchase #6 $238.39   10.537%   $263.5092   $263.51   $263.50   $263.50  
  Purchase #7 $49.53   10.736%   $54.8475   $54.85   $54.85   $54.80  
  7 purchase totals = $941.01       $1,013.6754   $1,013.67   $1,013.65   $1,013.70