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	$148.60	11.644%	$165.903	$165.90	$165.90	$165.90
Purchase #2	$88.90	5.181%	$93.5059	$93.51	$93.50	$93.50
Purchase #3	$137.41	10.264%	$151.5138	$151.51	$151.50	$151.50
Purchase #4	$132.61	11.550%	$147.9265	$147.93	$147.95	$147.90
Purchase #5	$139.63	5.868%	$147.8235	$147.82	$147.80	$147.80
Purchase #6	$79.58	4.381%	$83.0664	$83.07	$83.05	$83.10
Purchase #7	$154.28	9.600%	$169.0909	$169.09	$169.10	$169.10
7 purchase totals =	$881.01		$958.8300	$958.83	$958.80	$958.80