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 $67.84   11.657%   $75.7481   $75.75   $75.75   $75.70  
  Purchase #2 $95.65   12.123%   $107.2456   $107.25   $107.25   $107.20  
  Purchase #3 $49.66   13.172%   $56.2012   $56.20   $56.20   $56.20  
  Purchase #4 $101.29   5.491%   $106.8518   $106.85   $106.85   $106.90  
  Purchase #5 $20.85   5.411%   $21.9782   $21.98   $22.00   $22.00  
  Purchase #6 $76.35   9.680%   $83.7407   $83.74   $83.75   $83.70  
  Purchase #7 $191.31   6.563%   $203.8657   $203.87   $203.85   $203.90  
  7 purchase totals = $602.95       $655.6313   $655.64   $655.65   $655.60