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	$137.82	11.795%	$154.0759	$154.08	$154.10	$154.10
Purchase #2	$156.27	13.606%	$177.5321	$177.53	$177.55	$177.50
Purchase #3	$53.53	5.359%	$56.3987	$56.40	$56.40	$56.40
Purchase #4	$151.48	13.830%	$172.4297	$172.43	$172.45	$172.40
Purchase #5	$196.71	6.836%	$210.1571	$210.16	$210.15	$210.20
Purchase #6	$155.48	10.279%	$171.4618	$171.46	$171.45	$171.50
Purchase #7	$208.39	11.808%	$232.9967	$233.00	$233.00	$233.00
7 purchase totals =	$1,059.68		$1,175.0520	$1,175.06	$1,175.10	$1,175.10