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	$200.84	6.826%	$214.5493	$214.55	$214.55	$214.50
Purchase #2	$210.58	6.595%	$224.4678	$224.47	$224.45	$224.50
Purchase #3	$49.69	11.303%	$55.3065	$55.31	$55.30	$55.30
Purchase #4	$31.81	5.307%	$33.4982	$33.50	$33.50	$33.50
Purchase #5	$152.71	3.560%	$158.1465	$158.15	$158.15	$158.10
Purchase #6	$29.91	11.396%	$33.3185	$33.32	$33.30	$33.30
Purchase #7	$153.71	10.200%	$169.3884	$169.39	$169.40	$169.40
7 purchase totals =	$829.25		$888.6752	$888.69	$888.65	$888.60