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	$144.76	12.264%	$162.5134	$162.51	$162.50	$162.50
Purchase #2	$105.80	4.167%	$110.2087	$110.21	$110.20	$110.20
Purchase #3	$124.48	8.300%	$134.8118	$134.81	$134.80	$134.80
Purchase #4	$55.91	8.704%	$60.7764	$60.78	$60.80	$60.80
Purchase #5	$186.83	5.105%	$196.3677	$196.37	$196.35	$196.40
Purchase #6	$164.33	5.446%	$173.2794	$173.28	$173.30	$173.30
Purchase #7	$141.76	10.426%	$156.5399	$156.54	$156.55	$156.50
7 purchase totals =	$923.87		$994.4973	$994.50	$994.50	$994.50