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	$165.65	5.749%	$175.1732	$175.17	$175.15	$175.20
Purchase #2	$21.50	13.111%	$24.3189	$24.32	$24.30	$24.30
Purchase #3	$72.39	13.459%	$82.133	$82.13	$82.15	$82.10
Purchase #4	$208.26	9.641%	$228.3383	$228.34	$228.35	$228.30
Purchase #5	$146.32	3.621%	$151.6182	$151.62	$151.60	$151.60
Purchase #6	$30.71	8.793%	$33.4103	$33.41	$33.40	$33.40
Purchase #7	$17.52	7.342%	$18.8063	$18.81	$18.80	$18.80
7 purchase totals =	$662.35		$713.7982	$713.80	$713.75	$713.70