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	$212.87	3.113%	$219.4966	$219.50	$219.50	$219.50
Purchase #2	$26.85	7.159%	$28.7722	$28.77	$28.75	$28.80
Purchase #3	$14.33	9.523%	$15.6946	$15.69	$15.70	$15.70
Purchase #4	$55.89	10.202%	$61.5919	$61.59	$61.60	$61.60
Purchase #5	$28.90	13.166%	$32.705	$32.71	$32.70	$32.70
Purchase #6	$189.87	5.415%	$200.1515	$200.15	$200.15	$200.20
Purchase #7	$205.72	13.487%	$233.4655	$233.47	$233.45	$233.50
7 purchase totals =	$734.43		$791.8773	$791.88	$791.85	$792.00