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	$222.50	9.797%	$244.2983	$244.30	$244.30	$244.30
Purchase #2	$170.90	6.749%	$182.434	$182.43	$182.45	$182.40
Purchase #3	$151.90	13.685%	$172.6875	$172.69	$172.70	$172.70
Purchase #4	$195.54	10.321%	$215.7217	$215.72	$215.70	$215.70
Purchase #5	$129.83	5.568%	$137.0589	$137.06	$137.05	$137.10
Purchase #6	$195.52	9.169%	$213.4472	$213.45	$213.45	$213.40
Purchase #7	$25.85	11.141%	$28.7299	$28.73	$28.75	$28.70
7 purchase totals =	$1,092.04		$1,194.3775	$1,194.38	$1,194.40	$1,194.30