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	$196.42	8.752%	$213.6107	$213.61	$213.60	$213.60
Purchase #2	$240.75	11.429%	$268.2653	$268.27	$268.25	$268.30
Purchase #3	$166.74	11.401%	$185.75	$185.75	$185.75	$185.80
Purchase #4	$216.88	6.198%	$230.3222	$230.32	$230.30	$230.30
Purchase #5	$130.25	5.738%	$137.7237	$137.72	$137.70	$137.70
Purchase #6	$52.25	8.723%	$56.8078	$56.81	$56.80	$56.80
Purchase #7	$149.98	5.401%	$158.0804	$158.08	$158.10	$158.10
7 purchase totals =	$1,153.27		$1,250.5601	$1,250.56	$1,250.50	$1,250.60