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	$243.35	6.149%	$258.3136	$258.31	$258.30	$258.30
Purchase #2	$73.39	13.434%	$83.2492	$83.25	$83.25	$83.20
Purchase #3	$10.57	3.220%	$10.9104	$10.91	$10.90	$10.90
Purchase #4	$118.25	10.255%	$130.3765	$130.38	$130.40	$130.40
Purchase #5	$149.39	5.860%	$158.1443	$158.14	$158.15	$158.10
Purchase #6	$192.50	11.771%	$215.1592	$215.16	$215.15	$215.20
Purchase #7	$78.96	9.716%	$86.6318	$86.63	$86.65	$86.60
7 purchase totals =	$866.41		$942.7850	$942.78	$942.80	$942.70