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	$242.51	10.407%	$267.748	$267.75	$267.75	$267.70
Purchase #2	$239.78	4.344%	$250.196	$250.20	$250.20	$250.20
Purchase #3	$59.27	9.863%	$65.1158	$65.12	$65.10	$65.10
Purchase #4	$150.58	6.571%	$160.4746	$160.47	$160.45	$160.50
Purchase #5	$169.50	13.215%	$191.8994	$191.90	$191.90	$191.90
Purchase #6	$166.73	7.715%	$179.5932	$179.59	$179.60	$179.60
Purchase #7	$11.83	8.235%	$12.8042	$12.80	$12.80	$12.80
7 purchase totals =	$1,040.20		$1,127.8312	$1,127.83	$1,127.80	$1,127.80