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 $119.28   5.255%   $125.5482   $125.55   $125.55   $125.50  
  Purchase #2 $102.79   5.424%   $108.3653   $108.37   $108.35   $108.40  
  Purchase #3 $62.86   11.668%   $70.1945   $70.19   $70.20   $70.20  
  Purchase #4 $178.31   13.185%   $201.8202   $201.82   $201.80   $201.80  
  Purchase #5 $119.43   9.713%   $131.0302   $131.03   $131.05   $131.00  
  Purchase #6 $244.70   8.852%   $266.3608   $266.36   $266.35   $266.40  
  Purchase #7 $7.90   7.550%   $8.4965   $8.50   $8.50   $8.50  
  7 purchase totals = $835.27       $911.8157   $911.82   $911.80   $911.80