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	$56.57	13.712%	$64.3269	$64.33	$64.35	$64.30
Purchase #2	$70.25	9.432%	$76.876	$76.88	$76.90	$76.90
Purchase #3	$178.45	3.510%	$184.7136	$184.71	$184.70	$184.70
Purchase #4	$98.25	13.319%	$111.3359	$111.34	$111.35	$111.30
Purchase #5	$117.89	7.806%	$127.0925	$127.09	$127.10	$127.10
Purchase #6	$144.44	4.346%	$150.7174	$150.72	$150.70	$150.70
Purchase #7	$46.65	6.710%	$49.7802	$49.78	$49.80	$49.80
7 purchase totals =	$712.50		$764.8425	$764.85	$764.90	$764.80