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	$127.87	6.860%	$136.6419	$136.64	$136.65	$136.60
Purchase #2	$66.88	10.194%	$73.6977	$73.70	$73.70	$73.70
Purchase #3	$32.47	7.475%	$34.8971	$34.90	$34.90	$34.90
Purchase #4	$120.78	6.399%	$128.5087	$128.51	$128.50	$128.50
Purchase #5	$90.88	8.744%	$98.8265	$98.83	$98.85	$98.80
Purchase #6	$11.51	8.383%	$12.4749	$12.47	$12.45	$12.50
Purchase #7	$136.50	11.117%	$151.6747	$151.67	$151.65	$151.70
7 purchase totals =	$586.89		$636.7215	$636.72	$636.70	$636.70