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	$94.53	9.700%	$103.6994	$103.70	$103.70	$103.70
Purchase #2	$99.95	8.419%	$108.3648	$108.36	$108.35	$108.40
Purchase #3	$170.74	12.505%	$192.091	$192.09	$192.10	$192.10
Purchase #4	$129.50	11.621%	$144.5492	$144.55	$144.55	$144.50
Purchase #5	$45.83	9.791%	$50.3172	$50.32	$50.30	$50.30
Purchase #6	$49.60	8.291%	$53.7123	$53.71	$53.70	$53.70
Purchase #7	$105.57	6.569%	$112.5049	$112.50	$112.50	$112.50
7 purchase totals =	$695.72		$765.2388	$765.23	$765.20	$765.20