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	$66.69	7.524%	$71.7078	$71.71	$71.70	$71.70
Purchase #2	$60.52	13.410%	$68.6357	$68.64	$68.65	$68.60
Purchase #3	$85.53	4.531%	$89.4054	$89.41	$89.40	$89.40
Purchase #4	$172.32	13.139%	$194.9611	$194.96	$194.95	$195.00
Purchase #5	$53.31	12.247%	$59.8389	$59.84	$59.85	$59.80
Purchase #6	$74.98	13.646%	$85.2118	$85.21	$85.20	$85.20
Purchase #7	$167.68	3.471%	$173.5002	$173.50	$173.50	$173.50
7 purchase totals =	$681.03		$743.2609	$743.27	$743.25	$743.20