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 $23.46   3.426%   $24.2637   $24.26   $24.25   $24.30  
  Purchase #2 $229.98   9.709%   $252.3088   $252.31   $252.30   $252.30  
  Purchase #3 $31.73   7.251%   $34.0307   $34.03   $34.05   $34.00  
  Purchase #4 $159.37   8.251%   $172.5196   $172.52   $172.50   $172.50  
  Purchase #5 $194.27   6.388%   $206.68   $206.68   $206.70   $206.70  
  Purchase #6 $238.62   3.577%   $247.1554   $247.16   $247.15   $247.20  
  Purchase #7 $194.34   5.688%   $205.3941   $205.39   $205.40   $205.40  
  7 purchase totals = $1,071.77       $1,142.3523   $1,142.35   $1,142.35   $1,142.40