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	$101.41	9.853%	$111.4019	$111.40	$111.40	$111.40
Purchase #2	$158.57	7.525%	$170.5024	$170.50	$170.50	$170.50
Purchase #3	$214.26	10.408%	$236.5602	$236.56	$236.55	$236.60
Purchase #4	$97.77	3.339%	$101.0345	$101.03	$101.05	$101.00
Purchase #5	$64.63	13.372%	$73.2723	$73.27	$73.25	$73.30
Purchase #6	$134.98	7.364%	$144.9199	$144.92	$144.90	$144.90
Purchase #7	$115.82	10.164%	$127.5919	$127.59	$127.60	$127.60
7 purchase totals =	$887.44		$965.2831	$965.27	$965.25	$965.30