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	$17.87	4.365%	$18.65	$18.65	$18.65	$18.70
Purchase #2	$16.64	12.366%	$18.6977	$18.70	$18.70	$18.70
Purchase #3	$56.33	5.206%	$59.2625	$59.26	$59.25	$59.30
Purchase #4	$210.39	6.758%	$224.6082	$224.61	$224.60	$224.60
Purchase #5	$105.57	5.593%	$111.4745	$111.47	$111.45	$111.50
Purchase #6	$97.59	4.334%	$101.8196	$101.82	$101.80	$101.80
Purchase #7	$69.70	5.511%	$73.5412	$73.54	$73.55	$73.50
7 purchase totals =	$574.09		$608.0537	$608.05	$608.00	$608.10