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	$147.97	13.283%	$167.6249	$167.62	$167.60	$167.60
Purchase #2	$12.48	11.831%	$13.9565	$13.96	$13.95	$14.00
Purchase #3	$143.78	5.449%	$151.6146	$151.61	$151.60	$151.60
Purchase #4	$219.50	4.274%	$228.8814	$228.88	$228.90	$228.90
Purchase #5	$150.94	3.754%	$156.6063	$156.61	$156.60	$156.60
Purchase #6	$158.65	8.513%	$172.1559	$172.16	$172.15	$172.20
Purchase #7	$72.40	9.590%	$79.3432	$79.34	$79.35	$79.30
7 purchase totals =	$905.72		$970.1828	$970.18	$970.15	$970.20