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	$154.70	12.765%	$174.4475	$174.45	$174.45	$174.40
Purchase #2	$106.59	11.262%	$118.5942	$118.59	$118.60	$118.60
Purchase #3	$32.78	7.196%	$35.1388	$35.14	$35.15	$35.10
Purchase #4	$62.36	8.575%	$67.7074	$67.71	$67.70	$67.70
Purchase #5	$199.51	5.867%	$211.2153	$211.22	$211.20	$211.20
Purchase #6	$60.92	3.275%	$62.9151	$62.92	$62.90	$62.90
Purchase #7	$202.27	7.537%	$217.5151	$217.52	$217.50	$217.50
7 purchase totals =	$819.13		$887.5334	$887.55	$887.50	$887.40