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	$230.40	5.582%	$243.2609	$243.26	$243.25	$243.30
Purchase #2	$53.44	11.223%	$59.4376	$59.44	$59.45	$59.40
Purchase #3	$212.78	7.873%	$229.5322	$229.53	$229.55	$229.50
Purchase #4	$246.76	9.322%	$269.763	$269.76	$269.75	$269.80
Purchase #5	$128.54	3.274%	$132.7484	$132.75	$132.75	$132.70
Purchase #6	$173.91	9.105%	$189.7445	$189.74	$189.75	$189.70
Purchase #7	$100.31	10.693%	$111.0361	$111.04	$111.05	$111.00
7 purchase totals =	$1,146.14		$1,235.5227	$1,235.52	$1,235.55	$1,235.40