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	$172.45	4.283%	$179.836	$179.84	$179.85	$179.80
Purchase #2	$236.65	7.586%	$254.6023	$254.60	$254.60	$254.60
Purchase #3	$41.91	11.121%	$46.5708	$46.57	$46.55	$46.60
Purchase #4	$100.61	5.289%	$105.9313	$105.93	$105.95	$105.90
Purchase #5	$172.50	4.157%	$179.6708	$179.67	$179.65	$179.70
Purchase #6	$11.48	8.274%	$12.4299	$12.43	$12.45	$12.40
Purchase #7	$6.60	3.557%	$6.8348	$6.83	$6.85	$6.80
7 purchase totals =	$742.20		$785.8759	$785.87	$785.90	$785.80