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	$233.68	13.295%	$264.7478	$264.75	$264.75	$264.70
Purchase #2	$85.94	3.859%	$89.2564	$89.26	$89.25	$89.30
Purchase #3	$214.84	9.659%	$235.5914	$235.59	$235.60	$235.60
Purchase #4	$33.85	10.579%	$37.431	$37.43	$37.45	$37.40
Purchase #5	$103.27	13.578%	$117.292	$117.29	$117.30	$117.30
Purchase #6	$57.55	12.616%	$64.8105	$64.81	$64.80	$64.80
Purchase #7	$99.41	6.148%	$105.5217	$105.52	$105.50	$105.50
7 purchase totals =	$828.54		$914.6508	$914.65	$914.65	$914.60