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	$76.77	13.245%	$86.9382	$86.94	$86.95	$86.90
Purchase #2	$79.33	5.113%	$83.3861	$83.39	$83.40	$83.40
Purchase #3	$218.92	5.181%	$230.2622	$230.26	$230.25	$230.30
Purchase #4	$35.34	13.351%	$40.0582	$40.06	$40.05	$40.10
Purchase #5	$81.28	10.257%	$89.6169	$89.62	$89.60	$89.60
Purchase #6	$104.43	4.497%	$109.1262	$109.13	$109.15	$109.10
Purchase #7	$166.43	3.633%	$172.4764	$172.48	$172.50	$172.50
7 purchase totals =	$762.50		$811.8642	$811.88	$811.90	$811.90