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	$168.73	4.488%	$176.3026	$176.30	$176.30	$176.30
Purchase #2	$17.90	4.850%	$18.7682	$18.77	$18.75	$18.80
Purchase #3	$171.79	11.689%	$191.8705	$191.87	$191.85	$191.90
Purchase #4	$143.56	8.396%	$155.6133	$155.61	$155.60	$155.60
Purchase #5	$173.79	10.108%	$191.3567	$191.36	$191.35	$191.40
Purchase #6	$240.78	8.354%	$260.8948	$260.89	$260.90	$260.90
Purchase #7	$75.36	10.852%	$83.5381	$83.54	$83.55	$83.50
7 purchase totals =	$991.91		$1,078.3442	$1,078.34	$1,078.30	$1,078.40