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	$166.81	12.134%	$187.0507	$187.05	$187.05	$187.10
Purchase #2	$53.95	6.555%	$57.4864	$57.49	$57.50	$57.50
Purchase #3	$249.78	3.129%	$257.5956	$257.60	$257.60	$257.60
Purchase #4	$223.52	4.670%	$233.9584	$233.96	$233.95	$234.00
Purchase #5	$73.54	6.111%	$78.034	$78.03	$78.05	$78.00
Purchase #6	$111.58	4.790%	$116.9247	$116.92	$116.90	$116.90
Purchase #7	$205.86	13.228%	$233.0912	$233.09	$233.10	$233.10
7 purchase totals =	$1,085.04		$1,164.1410	$1,164.14	$1,164.15	$1,164.20