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	$144.68	12.173%	$162.2919	$162.29	$162.30	$162.30
Purchase #2	$33.43	6.134%	$35.4806	$35.48	$35.50	$35.50
Purchase #3	$167.42	6.597%	$178.4647	$178.46	$178.45	$178.50
Purchase #4	$141.74	13.542%	$160.9344	$160.93	$160.95	$160.90
Purchase #5	$101.44	8.277%	$109.8362	$109.84	$109.85	$109.80
Purchase #6	$167.45	10.475%	$184.9904	$184.99	$185.00	$185.00
Purchase #7	$222.43	7.138%	$238.3071	$238.31	$238.30	$238.30
7 purchase totals =	$978.59		$1,070.3053	$1,070.30	$1,070.35	$1,070.30