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	$191.54	10.102%	$210.8894	$210.89	$210.90	$210.90
Purchase #2	$132.33	9.283%	$144.6142	$144.61	$144.60	$144.60
Purchase #3	$53.85	13.579%	$61.1623	$61.16	$61.15	$61.20
Purchase #4	$153.87	6.380%	$163.6869	$163.69	$163.70	$163.70
Purchase #5	$127.38	10.523%	$140.7842	$140.78	$140.80	$140.80
Purchase #6	$124.38	10.411%	$137.3292	$137.33	$137.35	$137.30
Purchase #7	$188.54	9.653%	$206.7398	$206.74	$206.75	$206.70
7 purchase totals =	$971.89		$1,065.2060	$1,065.20	$1,065.25	$1,065.20