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	$210.63	11.772%	$235.4254	$235.43	$235.45	$235.40
Purchase #2	$141.70	7.305%	$152.0512	$152.05	$152.05	$152.10
Purchase #3	$102.69	8.654%	$111.5768	$111.58	$111.60	$111.60
Purchase #4	$222.75	5.591%	$235.204	$235.20	$235.20	$235.20
Purchase #5	$232.82	11.471%	$259.5268	$259.53	$259.55	$259.50
Purchase #6	$91.74	10.778%	$101.6277	$101.63	$101.65	$101.60
Purchase #7	$123.99	11.222%	$137.9042	$137.90	$137.90	$137.90
7 purchase totals =	$1,126.32		$1,233.3161	$1,233.32	$1,233.40	$1,233.30