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	$89.42	10.179%	$98.5221	$98.52	$98.50	$98.50
Purchase #2	$165.26	8.860%	$179.902	$179.90	$179.90	$179.90
Purchase #3	$242.58	5.739%	$256.5017	$256.50	$256.50	$256.50
Purchase #4	$99.85	10.489%	$110.3233	$110.32	$110.30	$110.30
Purchase #5	$167.55	3.433%	$173.302	$173.30	$173.30	$173.30
Purchase #6	$162.83	12.464%	$183.1251	$183.13	$183.15	$183.10
Purchase #7	$64.61	3.616%	$66.9463	$66.95	$66.95	$66.90
7 purchase totals =	$992.10		$1,068.6225	$1,068.62	$1,068.60	$1,068.50