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	$30.27	13.845%	$34.4609	$34.46	$34.45	$34.50
Purchase #2	$195.59	13.627%	$222.243	$222.24	$222.25	$222.20
Purchase #3	$47.43	4.363%	$49.4994	$49.50	$49.50	$49.50
Purchase #4	$139.69	7.308%	$149.8985	$149.90	$149.90	$149.90
Purchase #5	$151.62	3.783%	$157.3558	$157.36	$157.35	$157.40
Purchase #6	$163.69	6.250%	$173.9206	$173.92	$173.90	$173.90
Purchase #7	$209.40	9.616%	$229.5359	$229.54	$229.55	$229.50
7 purchase totals =	$937.69		$1,016.9141	$1,016.92	$1,016.90	$1,016.90