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	$140.47	5.385%	$148.0343	$148.03	$148.05	$148.00
Purchase #2	$176.30	13.857%	$200.7299	$200.73	$200.75	$200.70
Purchase #3	$113.46	3.539%	$117.4753	$117.48	$117.50	$117.50
Purchase #4	$188.58	4.251%	$196.5965	$196.60	$196.60	$196.60
Purchase #5	$83.84	7.624%	$90.232	$90.23	$90.25	$90.20
Purchase #6	$42.45	7.278%	$45.5395	$45.54	$45.55	$45.50
Purchase #7	$123.67	6.540%	$131.758	$131.76	$131.75	$131.80
7 purchase totals =	$868.77		$930.3655	$930.37	$930.45	$930.30