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	$81.45	6.498%	$86.7426	$86.74	$86.75	$86.70
Purchase #2	$185.57	13.457%	$210.5422	$210.54	$210.55	$210.50
Purchase #3	$223.30	3.475%	$231.0597	$231.06	$231.05	$231.10
Purchase #4	$81.29	7.500%	$87.3868	$87.39	$87.40	$87.40
Purchase #5	$161.64	5.230%	$170.0938	$170.09	$170.10	$170.10
Purchase #6	$191.74	10.848%	$212.54	$212.54	$212.55	$212.50
Purchase #7	$95.44	4.211%	$99.459	$99.46	$99.45	$99.50
7 purchase totals =	$1,020.43		$1,097.8241	$1,097.82	$1,097.85	$1,097.80