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	$202.87	13.746%	$230.7565	$230.76	$230.75	$230.80
Purchase #2	$19.27	5.631%	$20.3551	$20.36	$20.35	$20.40
Purchase #3	$74.76	5.240%	$78.6774	$78.68	$78.70	$78.70
Purchase #4	$230.78	3.315%	$238.4304	$238.43	$238.45	$238.40
Purchase #5	$150.48	11.745%	$168.1539	$168.15	$168.15	$168.20
Purchase #6	$165.51	8.158%	$179.0123	$179.01	$179.00	$179.00
Purchase #7	$36.58	8.739%	$39.7767	$39.78	$39.80	$39.80
7 purchase totals =	$880.25		$955.1623	$955.17	$955.20	$955.30