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	$228.38	8.785%	$248.4432	$248.44	$248.45	$248.40
Purchase #2	$143.60	3.484%	$148.603	$148.60	$148.60	$148.60
Purchase #3	$67.39	11.110%	$74.877	$74.88	$74.90	$74.90
Purchase #4	$191.51	4.183%	$199.5209	$199.52	$199.50	$199.50
Purchase #5	$222.37	7.366%	$238.7498	$238.75	$238.75	$238.70
Purchase #6	$49.73	6.525%	$52.9749	$52.97	$52.95	$53.00
Purchase #7	$158.25	6.341%	$168.2846	$168.28	$168.30	$168.30
7 purchase totals =	$1,061.23		$1,131.4534	$1,131.44	$1,131.45	$1,131.40