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	$40.60	6.266%	$43.144	$43.14	$43.15	$43.10
Purchase #2	$75.39	12.751%	$85.003	$85.00	$85.00	$85.00
Purchase #3	$156.96	5.451%	$165.5159	$165.52	$165.50	$165.50
Purchase #4	$73.60	13.418%	$83.4756	$83.48	$83.50	$83.50
Purchase #5	$83.28	7.342%	$89.3944	$89.39	$89.40	$89.40
Purchase #6	$38.35	13.733%	$43.6166	$43.62	$43.60	$43.60
Purchase #7	$195.30	8.334%	$211.5763	$211.58	$211.60	$211.60
7 purchase totals =	$663.48		$721.7258	$721.73	$721.75	$721.70