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	$241.50	6.349%	$256.8328	$256.83	$256.85	$256.80
Purchase #2	$70.32	10.334%	$77.5869	$77.59	$77.60	$77.60
Purchase #3	$26.46	12.464%	$29.758	$29.76	$29.75	$29.80
Purchase #4	$80.67	11.250%	$89.7454	$89.75	$89.75	$89.70
Purchase #5	$13.39	6.543%	$14.2661	$14.27	$14.25	$14.30
Purchase #6	$215.54	13.315%	$244.2392	$244.24	$244.25	$244.20
Purchase #7	$193.73	8.181%	$209.5791	$209.58	$209.60	$209.60
7 purchase totals =	$841.61		$922.0075	$922.02	$922.05	$922.00