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 $84.82   11.555%   $94.621   $94.62   $94.60   $94.60  
  Purchase #2 $57.52   3.689%   $59.6419   $59.64   $59.65   $59.60  
  Purchase #3 $202.84   6.751%   $216.5337   $216.53   $216.55   $216.50  
  Purchase #4 $72.51   5.213%   $76.2899   $76.29   $76.30   $76.30  
  Purchase #5 $208.49   9.199%   $227.669   $227.67   $227.65   $227.70  
  Purchase #6 $173.85   4.130%   $181.03   $181.03   $181.05   $181.00  
  Purchase #7 $156.72   8.252%   $169.6525   $169.65   $169.65   $169.70  
  7 purchase totals = $956.75       $1,025.4380   $1,025.43   $1,025.45   $1,025.40