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	$114.99	8.331%	$124.5698	$124.57	$124.55	$124.60
Purchase #2	$10.52	9.504%	$11.5198	$11.52	$11.50	$11.50
Purchase #3	$37.69	10.800%	$41.7605	$41.76	$41.75	$41.80
Purchase #4	$142.97	5.245%	$150.4688	$150.47	$150.45	$150.50
Purchase #5	$131.89	10.169%	$145.3019	$145.30	$145.30	$145.30
Purchase #6	$42.65	8.183%	$46.14	$46.14	$46.15	$46.10
Purchase #7	$64.42	10.766%	$71.3555	$71.36	$71.35	$71.40
7 purchase totals =	$545.13		$591.1163	$591.12	$591.05	$591.20