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	$212.99	10.359%	$235.0536	$235.05	$235.05	$235.10
Purchase #2	$48.76	12.282%	$54.7487	$54.75	$54.75	$54.70
Purchase #3	$88.77	13.258%	$100.5391	$100.54	$100.55	$100.50
Purchase #4	$160.53	13.543%	$182.2706	$182.27	$182.25	$182.30
Purchase #5	$47.89	7.540%	$51.5009	$51.50	$51.50	$51.50
Purchase #6	$61.45	4.476%	$64.2005	$64.20	$64.20	$64.20
Purchase #7	$37.64	13.851%	$42.8535	$42.85	$42.85	$42.90
7 purchase totals =	$658.03		$731.1669	$731.16	$731.15	$731.20