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	$104.54	12.237%	$117.3326	$117.33	$117.35	$117.30
Purchase #2	$222.32	7.249%	$238.436	$238.44	$238.45	$238.40
Purchase #3	$147.43	5.334%	$155.2939	$155.29	$155.30	$155.30
Purchase #4	$144.68	6.203%	$153.6545	$153.65	$153.65	$153.70
Purchase #5	$179.86	4.793%	$188.4807	$188.48	$188.50	$188.50
Purchase #6	$230.48	4.385%	$240.5865	$240.59	$240.60	$240.60
Purchase #7	$14.39	7.755%	$15.5059	$15.51	$15.50	$15.50
7 purchase totals =	$1,043.70		$1,109.2901	$1,109.29	$1,109.35	$1,109.30