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	$12.94	8.474%	$14.0365	$14.04	$14.05	$14.00
Purchase #2	$53.85	4.294%	$56.1623	$56.16	$56.15	$56.20
Purchase #3	$165.53	11.514%	$184.5891	$184.59	$184.60	$184.60
Purchase #4	$168.71	10.191%	$185.9032	$185.90	$185.90	$185.90
Purchase #5	$106.33	4.402%	$111.0106	$111.01	$111.00	$111.00
Purchase #6	$61.85	13.283%	$70.0655	$70.07	$70.05	$70.10
Purchase #7	$17.74	5.687%	$18.7489	$18.75	$18.75	$18.70
7 purchase totals =	$586.95		$640.5161	$640.52	$640.50	$640.50