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	$151.34	11.190%	$168.2749	$168.27	$168.25	$168.30
Purchase #2	$62.37	3.244%	$64.3933	$64.39	$64.40	$64.40
Purchase #3	$55.84	9.259%	$61.0102	$61.01	$61.00	$61.00
Purchase #4	$137.26	11.863%	$153.5432	$153.54	$153.55	$153.50
Purchase #5	$51.40	8.281%	$55.6564	$55.66	$55.65	$55.70
Purchase #6	$228.71	6.447%	$243.4549	$243.45	$243.45	$243.50
Purchase #7	$160.54	3.173%	$165.6339	$165.63	$165.65	$165.60
7 purchase totals =	$847.46		$911.9668	$911.95	$911.95	$912.00