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	$151.81	11.716%	$169.5961	$169.60	$169.60	$169.60
Purchase #2	$7.78	8.221%	$8.4196	$8.42	$8.40	$8.40
Purchase #3	$99.87	13.285%	$113.1377	$113.14	$113.15	$113.10
Purchase #4	$20.77	3.600%	$21.5177	$21.52	$21.50	$21.50
Purchase #5	$123.37	3.830%	$128.0951	$128.10	$128.10	$128.10
Purchase #6	$73.51	12.707%	$82.8509	$82.85	$82.85	$82.90
Purchase #7	$159.85	5.188%	$168.143	$168.14	$168.15	$168.10
7 purchase totals =	$636.96		$691.7601	$691.77	$691.75	$691.70