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	$98.76	12.769%	$111.3707	$111.37	$111.35	$111.40
Purchase #2	$59.45	6.483%	$63.3041	$63.30	$63.30	$63.30
Purchase #3	$7.31	4.486%	$7.6379	$7.64	$7.65	$7.60
Purchase #4	$54.73	10.114%	$60.2654	$60.27	$60.25	$60.30
Purchase #5	$243.47	13.826%	$277.1322	$277.13	$277.15	$277.10
Purchase #6	$41.44	11.244%	$46.0995	$46.10	$46.10	$46.10
Purchase #7	$136.48	12.639%	$153.7297	$153.73	$153.75	$153.70
7 purchase totals =	$641.64		$719.5395	$719.54	$719.55	$719.50