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	$59.25	13.773%	$67.4105	$67.41	$67.40	$67.40
Purchase #2	$116.94	4.805%	$122.559	$122.56	$122.55	$122.60
Purchase #3	$175.37	6.392%	$186.5797	$186.58	$186.60	$186.60
Purchase #4	$179.27	4.330%	$187.0324	$187.03	$187.05	$187.00
Purchase #5	$105.39	5.535%	$111.2233	$111.22	$111.20	$111.20
Purchase #6	$209.41	6.362%	$222.7327	$222.73	$222.75	$222.70
Purchase #7	$53.25	6.608%	$56.7688	$56.77	$56.75	$56.80
7 purchase totals =	$898.88		$954.3064	$954.30	$954.30	$954.30