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	$29.66	8.114%	$32.0666	$32.07	$32.05	$32.10
Purchase #2	$190.59	10.771%	$211.1184	$211.12	$211.10	$211.10
Purchase #3	$199.50	10.230%	$219.9089	$219.91	$219.90	$219.90
Purchase #4	$53.64	11.276%	$59.6884	$59.69	$59.70	$59.70
Purchase #5	$75.32	3.677%	$78.0895	$78.09	$78.10	$78.10
Purchase #6	$145.95	5.729%	$154.3115	$154.31	$154.30	$154.30
Purchase #7	$154.43	11.635%	$172.3979	$172.40	$172.40	$172.40
7 purchase totals =	$849.09		$927.5812	$927.59	$927.55	$927.60