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	$47.97	13.248%	$54.3251	$54.33	$54.35	$54.30
Purchase #2	$168.43	12.282%	$189.1166	$189.12	$189.10	$189.10
Purchase #3	$109.43	12.419%	$123.0201	$123.02	$123.00	$123.00
Purchase #4	$16.37	5.389%	$17.2522	$17.25	$17.25	$17.30
Purchase #5	$150.45	3.430%	$155.6104	$155.61	$155.60	$155.60
Purchase #6	$12.77	9.158%	$13.9395	$13.94	$13.95	$13.90
Purchase #7	$231.42	7.551%	$248.8945	$248.89	$248.90	$248.90
7 purchase totals =	$736.84		$802.1584	$802.16	$802.15	$802.10