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	$212.72	8.831%	$231.5053	$231.51	$231.50	$231.50
Purchase #2	$66.51	9.211%	$72.6362	$72.64	$72.65	$72.60
Purchase #3	$89.31	3.819%	$92.7207	$92.72	$92.70	$92.70
Purchase #4	$9.75	7.442%	$10.4756	$10.48	$10.50	$10.50
Purchase #5	$231.41	11.473%	$257.9597	$257.96	$257.95	$258.00
Purchase #6	$209.28	6.725%	$223.3541	$223.35	$223.35	$223.40
Purchase #7	$79.76	13.478%	$90.5101	$90.51	$90.50	$90.50
7 purchase totals =	$898.74		$979.1617	$979.17	$979.15	$979.20