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	$178.41	6.848%	$190.6275	$190.63	$190.65	$190.60
Purchase #2	$74.95	6.740%	$80.0016	$80.00	$80.00	$80.00
Purchase #3	$5.67	10.361%	$6.2575	$6.26	$6.25	$6.30
Purchase #4	$146.46	3.155%	$151.0808	$151.08	$151.10	$151.10
Purchase #5	$173.86	6.184%	$184.6115	$184.61	$184.60	$184.60
Purchase #6	$19.46	3.402%	$20.122	$20.12	$20.10	$20.10
Purchase #7	$105.26	6.299%	$111.8903	$111.89	$111.90	$111.90
7 purchase totals =	$704.07		$744.5912	$744.59	$744.60	$744.60