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	$60.76	6.471%	$64.6918	$64.69	$64.70	$64.70
Purchase #2	$51.56	7.251%	$55.2986	$55.30	$55.30	$55.30
Purchase #3	$99.80	11.488%	$111.265	$111.27	$111.25	$111.30
Purchase #4	$9.28	13.488%	$10.5317	$10.53	$10.55	$10.50
Purchase #5	$200.31	4.559%	$209.4421	$209.44	$209.45	$209.40
Purchase #6	$183.39	11.693%	$204.8338	$204.83	$204.85	$204.80
Purchase #7	$21.45	3.718%	$22.2475	$22.25	$22.25	$22.20
7 purchase totals =	$626.55		$678.3105	$678.31	$678.35	$678.20