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 $59.37   5.556%   $62.6686   $62.67   $62.65   $62.70  
  Purchase #2 $41.96   11.452%   $46.7653   $46.77   $46.75   $46.80  
  Purchase #3 $6.68   9.123%   $7.2894   $7.29   $7.30   $7.30  
  Purchase #4 $201.39   9.187%   $219.8917   $219.89   $219.90   $219.90  
  Purchase #5 $163.49   7.774%   $176.1997   $176.20   $176.20   $176.20  
  Purchase #6 $21.80   9.252%   $23.8169   $23.82   $23.80   $23.80  
  Purchase #7 $195.64   12.163%   $219.4357   $219.44   $219.45   $219.40  
  7 purchase totals = $690.33       $756.0673   $756.08   $756.05   $756.10