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	$56.86	9.799%	$62.4317	$62.43	$62.45	$62.40
Purchase #2	$175.77	8.385%	$190.5083	$190.51	$190.50	$190.50
Purchase #3	$85.66	4.480%	$89.4976	$89.50	$89.50	$89.50
Purchase #4	$64.31	13.765%	$73.1623	$73.16	$73.15	$73.20
Purchase #5	$68.39	4.322%	$71.3458	$71.35	$71.35	$71.30
Purchase #6	$231.26	4.473%	$241.6043	$241.60	$241.60	$241.60
Purchase #7	$105.78	10.363%	$116.742	$116.74	$116.75	$116.70
7 purchase totals =	$788.03		$845.2920	$845.29	$845.30	$845.20