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	$147.60	10.271%	$162.76	$162.76	$162.75	$162.80
Purchase #2	$50.65	9.345%	$55.3832	$55.38	$55.40	$55.40
Purchase #3	$24.90	13.747%	$28.323	$28.32	$28.30	$28.30
Purchase #4	$209.77	13.275%	$237.617	$237.62	$237.60	$237.60
Purchase #5	$78.90	13.522%	$89.5689	$89.57	$89.55	$89.60
Purchase #6	$132.61	5.235%	$139.5521	$139.55	$139.55	$139.60
Purchase #7	$158.98	9.251%	$173.6872	$173.69	$173.70	$173.70
7 purchase totals =	$803.41		$886.8914	$886.89	$886.85	$887.00