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	$238.61	10.649%	$264.0196	$264.02	$264.00	$264.00
Purchase #2	$191.85	6.654%	$204.6157	$204.62	$204.60	$204.60
Purchase #3	$19.48	4.619%	$20.3798	$20.38	$20.40	$20.40
Purchase #4	$38.49	9.479%	$42.1385	$42.14	$42.15	$42.10
Purchase #5	$144.55	12.491%	$162.6057	$162.61	$162.60	$162.60
Purchase #6	$185.65	13.594%	$210.8873	$210.89	$210.90	$210.90
Purchase #7	$132.63	3.834%	$137.715	$137.72	$137.70	$137.70
7 purchase totals =	$951.26		$1,042.3616	$1,042.38	$1,042.35	$1,042.30