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	$133.71	12.521%	$150.4518	$150.45	$150.45	$150.50
Purchase #2	$46.52	4.123%	$48.438	$48.44	$48.45	$48.40
Purchase #3	$50.33	4.437%	$52.5631	$52.56	$52.55	$52.60
Purchase #4	$157.48	10.377%	$173.8217	$173.82	$173.80	$173.80
Purchase #5	$230.42	10.634%	$254.9229	$254.92	$254.90	$254.90
Purchase #6	$167.32	4.391%	$174.667	$174.67	$174.65	$174.70
Purchase #7	$152.76	11.654%	$170.5627	$170.56	$170.55	$170.60
7 purchase totals =	$938.54		$1,025.4272	$1,025.42	$1,025.35	$1,025.50