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	$144.86	4.508%	$151.3903	$151.39	$151.40	$151.40
Purchase #2	$67.84	4.716%	$71.0393	$71.04	$71.05	$71.00
Purchase #3	$184.67	3.373%	$190.8989	$190.90	$190.90	$190.90
Purchase #4	$108.62	8.535%	$117.8907	$117.89	$117.90	$117.90
Purchase #5	$68.37	4.793%	$71.647	$71.65	$71.65	$71.60
Purchase #6	$205.30	13.253%	$232.5084	$232.51	$232.50	$232.50
Purchase #7	$207.74	13.678%	$236.1547	$236.15	$236.15	$236.20
7 purchase totals =	$987.40		$1,071.5293	$1,071.53	$1,071.55	$1,071.50