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	$228.85	13.611%	$259.9988	$260.00	$260.00	$260.00
Purchase #2	$12.33	8.522%	$13.3808	$13.38	$13.40	$13.40
Purchase #3	$136.75	10.570%	$151.2045	$151.20	$151.20	$151.20
Purchase #4	$147.78	11.863%	$165.3111	$165.31	$165.30	$165.30
Purchase #5	$166.31	13.236%	$188.3228	$188.32	$188.30	$188.30
Purchase #6	$128.62	13.571%	$146.075	$146.08	$146.10	$146.10
Purchase #7	$210.47	6.677%	$224.5231	$224.52	$224.50	$224.50
7 purchase totals =	$1,031.11		$1,148.8161	$1,148.81	$1,148.80	$1,148.80