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	$200.92	10.109%	$221.231	$221.23	$221.25	$221.20
Purchase #2	$71.52	6.461%	$76.1409	$76.14	$76.15	$76.10
Purchase #3	$76.56	11.682%	$85.5037	$85.50	$85.50	$85.50
Purchase #4	$230.76	5.378%	$243.1703	$243.17	$243.15	$243.20
Purchase #5	$29.25	4.556%	$30.5826	$30.58	$30.60	$30.60
Purchase #6	$54.64	3.829%	$56.7322	$56.73	$56.75	$56.70
Purchase #7	$40.92	12.208%	$45.9155	$45.92	$45.90	$45.90
7 purchase totals =	$704.57		$759.2762	$759.27	$759.30	$759.20