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	$141.91	4.259%	$147.9539	$147.95	$147.95	$148.00
Purchase #2	$89.26	11.259%	$99.3098	$99.31	$99.30	$99.30
Purchase #3	$125.70	4.326%	$131.1378	$131.14	$131.15	$131.10
Purchase #4	$63.78	13.300%	$72.2627	$72.26	$72.25	$72.30
Purchase #5	$160.62	10.572%	$177.6007	$177.60	$177.60	$177.60
Purchase #6	$241.45	3.234%	$249.2585	$249.26	$249.25	$249.30
Purchase #7	$24.47	13.532%	$27.7813	$27.78	$27.80	$27.80
7 purchase totals =	$847.19		$905.3047	$905.30	$905.30	$905.40