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	$62.76	7.253%	$67.312	$67.31	$67.30	$67.30
Purchase #2	$184.25	4.293%	$192.1599	$192.16	$192.15	$192.20
Purchase #3	$152.87	5.707%	$161.5943	$161.59	$161.60	$161.60
Purchase #4	$159.67	9.263%	$174.4602	$174.46	$174.45	$174.50
Purchase #5	$158.60	9.870%	$174.2538	$174.25	$174.25	$174.30
Purchase #6	$158.62	9.867%	$174.271	$174.27	$174.25	$174.30
Purchase #7	$45.40	11.443%	$50.5951	$50.60	$50.60	$50.60
7 purchase totals =	$922.17		$994.6463	$994.64	$994.60	$994.80