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	$219.60	6.756%	$234.4362	$234.44	$234.45	$234.40
Purchase #2	$127.92	6.515%	$136.254	$136.25	$136.25	$136.30
Purchase #3	$19.57	10.104%	$21.5474	$21.55	$21.55	$21.50
Purchase #4	$156.61	5.706%	$165.5462	$165.55	$165.55	$165.50
Purchase #5	$53.84	13.610%	$61.1676	$61.17	$61.15	$61.20
Purchase #6	$182.35	12.441%	$205.0362	$205.04	$205.05	$205.00
Purchase #7	$79.97	4.404%	$83.4919	$83.49	$83.50	$83.50
7 purchase totals =	$839.86		$907.4795	$907.49	$907.50	$907.40