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	$190.64	6.461%	$202.9573	$202.96	$202.95	$203.00
Purchase #2	$100.96	10.826%	$111.8899	$111.89	$111.90	$111.90
Purchase #3	$147.60	3.230%	$152.3675	$152.37	$152.35	$152.40
Purchase #4	$193.37	8.156%	$209.1413	$209.14	$209.15	$209.10
Purchase #5	$107.66	4.554%	$112.5628	$112.56	$112.55	$112.60
Purchase #6	$40.67	3.525%	$42.1036	$42.10	$42.10	$42.10
Purchase #7	$115.72	5.304%	$121.8578	$121.86	$121.85	$121.90
7 purchase totals =	$896.62		$952.8802	$952.88	$952.85	$953.00