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 $212.88   13.490%   $241.5975   $241.60   $241.60   $241.60  
  Purchase #2 $184.38   4.773%   $193.1805   $193.18   $193.20   $193.20  
  Purchase #3 $237.71   4.135%   $247.5393   $247.54   $247.55   $247.50  
  Purchase #4 $97.84   11.128%   $108.7276   $108.73   $108.75   $108.70  
  Purchase #5 $192.47   6.781%   $205.5214   $205.52   $205.50   $205.50  
  Purchase #6 $42.79   5.832%   $45.2855   $45.29   $45.30   $45.30  
  Purchase #7 $115.97   7.173%   $124.2885   $124.29   $124.30   $124.30  
  7 purchase totals = $1,084.04       $1,166.1403   $1,166.15   $1,166.20   $1,166.10