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	$198.33	3.173%	$204.623	$204.62	$204.60	$204.60
Purchase #2	$123.80	3.105%	$127.644	$127.64	$127.65	$127.60
Purchase #3	$176.36	11.419%	$196.4985	$196.50	$196.50	$196.50
Purchase #4	$115.27	6.145%	$122.3533	$122.35	$122.35	$122.40
Purchase #5	$247.77	10.727%	$274.3483	$274.35	$274.35	$274.30
Purchase #6	$185.67	5.831%	$196.4964	$196.50	$196.50	$196.50
Purchase #7	$108.39	13.808%	$123.3565	$123.36	$123.35	$123.40
7 purchase totals =	$1,155.59		$1,245.3200	$1,245.32	$1,245.30	$1,245.30