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	$148.77	5.575%	$157.0639	$157.06	$157.05	$157.10
Purchase #2	$218.96	5.403%	$230.7904	$230.79	$230.80	$230.80
Purchase #3	$190.39	3.429%	$196.9185	$196.92	$196.90	$196.90
Purchase #4	$127.50	7.318%	$136.8305	$136.83	$136.85	$136.80
Purchase #5	$50.38	10.384%	$55.6115	$55.61	$55.60	$55.60
Purchase #6	$232.64	6.272%	$247.2312	$247.23	$247.25	$247.20
Purchase #7	$240.27	10.760%	$266.1231	$266.12	$266.10	$266.10
7 purchase totals =	$1,208.91		$1,290.5691	$1,290.56	$1,290.55	$1,290.50