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 $67.95   10.789%   $75.2811   $75.28   $75.30   $75.30  
  Purchase #2 $142.28   12.185%   $159.6168   $159.62   $159.60   $159.60  
  Purchase #3 $141.62   10.213%   $156.0837   $156.08   $156.10   $156.10  
  Purchase #4 $195.31   3.387%   $201.9251   $201.93   $201.95   $201.90  
  Purchase #5 $191.97   13.710%   $218.2891   $218.29   $218.30   $218.30  
  Purchase #6 $115.86   11.575%   $129.2708   $129.27   $129.25   $129.30  
  Purchase #7 $229.93   4.720%   $240.7827   $240.78   $240.80   $240.80  
  7 purchase totals = $1,084.92       $1,181.2493   $1,181.25   $1,181.30   $1,181.30