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	$156.41	7.164%	$167.6152	$167.62	$167.60	$167.60
Purchase #2	$30.82	5.556%	$32.5324	$32.53	$32.55	$32.50
Purchase #3	$140.32	12.789%	$158.2655	$158.27	$158.25	$158.30
Purchase #4	$175.78	6.813%	$187.7559	$187.76	$187.75	$187.80
Purchase #5	$127.88	7.250%	$137.1513	$137.15	$137.15	$137.20
Purchase #6	$157.81	5.109%	$165.8725	$165.87	$165.85	$165.90
Purchase #7	$208.78	7.533%	$224.5074	$224.51	$224.50	$224.50
7 purchase totals =	$997.80		$1,073.7002	$1,073.71	$1,073.65	$1,073.80