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	$79.54	6.721%	$84.8859	$84.89	$84.90	$84.90
Purchase #2	$180.82	7.657%	$194.6654	$194.67	$194.65	$194.70
Purchase #3	$91.65	4.592%	$95.8586	$95.86	$95.85	$95.90
Purchase #4	$223.48	8.255%	$241.9283	$241.93	$241.95	$241.90
Purchase #5	$53.29	6.538%	$56.7741	$56.77	$56.75	$56.80
Purchase #6	$144.90	6.833%	$154.801	$154.80	$154.80	$154.80
Purchase #7	$169.90	12.369%	$190.9149	$190.91	$190.90	$190.90
7 purchase totals =	$943.58		$1,019.8282	$1,019.83	$1,019.80	$1,019.90