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	$153.61	13.126%	$173.7728	$173.77	$173.75	$173.80
Purchase #2	$109.52	3.597%	$113.4594	$113.46	$113.45	$113.50
Purchase #3	$154.86	5.716%	$163.7118	$163.71	$163.70	$163.70
Purchase #4	$89.92	13.314%	$101.8919	$101.89	$101.90	$101.90
Purchase #5	$137.34	9.302%	$150.1154	$150.12	$150.10	$150.10
Purchase #6	$134.75	5.761%	$142.5129	$142.51	$142.50	$142.50
Purchase #7	$117.91	8.822%	$128.312	$128.31	$128.30	$128.30
7 purchase totals =	$897.91		$973.7762	$973.77	$973.70	$973.80