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	$157.56	10.196%	$173.6248	$173.62	$173.60	$173.60
Purchase #2	$247.89	5.532%	$261.6033	$261.60	$261.60	$261.60
Purchase #3	$238.87	8.146%	$258.3284	$258.33	$258.35	$258.30
Purchase #4	$88.27	10.831%	$97.8305	$97.83	$97.85	$97.80
Purchase #5	$74.63	10.835%	$82.7162	$82.72	$82.70	$82.70
Purchase #6	$175.73	3.248%	$181.4377	$181.44	$181.45	$181.40
Purchase #7	$222.35	7.234%	$238.4348	$238.43	$238.45	$238.40
7 purchase totals =	$1,205.30		$1,293.9757	$1,293.97	$1,294.00	$1,293.80