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	$146.75	7.503%	$157.7607	$157.76	$157.75	$157.80
Purchase #2	$144.37	4.256%	$150.5144	$150.51	$150.50	$150.50
Purchase #3	$205.75	6.162%	$218.4283	$218.43	$218.45	$218.40
Purchase #4	$6.70	13.308%	$7.5916	$7.59	$7.60	$7.60
Purchase #5	$18.68	10.675%	$20.6741	$20.67	$20.65	$20.70
Purchase #6	$244.60	7.820%	$263.7277	$263.73	$263.75	$263.70
Purchase #7	$34.47	10.737%	$38.171	$38.17	$38.15	$38.20
7 purchase totals =	$801.32		$856.8678	$856.86	$856.85	$856.90