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	$158.95	5.697%	$168.0054	$168.01	$168.00	$168.00
Purchase #2	$182.60	7.627%	$196.5269	$196.53	$196.55	$196.50
Purchase #3	$244.77	9.729%	$268.5837	$268.58	$268.60	$268.60
Purchase #4	$6.75	6.261%	$7.1726	$7.17	$7.15	$7.20
Purchase #5	$177.40	9.585%	$194.4038	$194.40	$194.40	$194.40
Purchase #6	$206.31	11.560%	$230.1594	$230.16	$230.15	$230.20
Purchase #7	$86.64	3.710%	$89.8543	$89.85	$89.85	$89.90
7 purchase totals =	$1,063.42		$1,154.7061	$1,154.70	$1,154.70	$1,154.80