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	$146.40	3.711%	$151.8329	$151.83	$151.85	$151.80
Purchase #2	$65.79	13.364%	$74.5822	$74.58	$74.60	$74.60
Purchase #3	$54.89	7.516%	$59.0155	$59.02	$59.00	$59.00
Purchase #4	$103.55	3.255%	$106.9206	$106.92	$106.90	$106.90
Purchase #5	$50.42	6.520%	$53.7074	$53.71	$53.70	$53.70
Purchase #6	$47.50	13.218%	$53.7786	$53.78	$53.80	$53.80
Purchase #7	$160.93	5.572%	$169.897	$169.90	$169.90	$169.90
7 purchase totals =	$629.48		$669.7342	$669.74	$669.75	$669.70