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	$240.77	4.570%	$251.7732	$251.77	$251.75	$251.80
Purchase #2	$193.83	6.628%	$206.6771	$206.68	$206.70	$206.70
Purchase #3	$165.93	4.432%	$173.284	$173.28	$173.30	$173.30
Purchase #4	$31.53	11.503%	$35.1569	$35.16	$35.15	$35.20
Purchase #5	$132.54	10.515%	$146.4766	$146.48	$146.50	$146.50
Purchase #6	$237.47	3.390%	$245.5202	$245.52	$245.50	$245.50
Purchase #7	$102.91	6.479%	$109.5775	$109.58	$109.60	$109.60
7 purchase totals =	$1,104.98		$1,168.4655	$1,168.47	$1,168.50	$1,168.60