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	$247.46	7.836%	$266.851	$266.85	$266.85	$266.90
Purchase #2	$66.71	13.265%	$75.5591	$75.56	$75.55	$75.60
Purchase #3	$37.87	5.797%	$40.0653	$40.07	$40.05	$40.10
Purchase #4	$210.30	10.225%	$231.8032	$231.80	$231.80	$231.80
Purchase #5	$32.95	12.473%	$37.0599	$37.06	$37.05	$37.10
Purchase #6	$110.82	11.612%	$123.6884	$123.69	$123.70	$123.70
Purchase #7	$55.26	9.308%	$60.4036	$60.40	$60.40	$60.40
7 purchase totals =	$761.37		$835.4305	$835.43	$835.40	$835.60