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	$148.76	3.394%	$153.8089	$153.81	$153.80	$153.80
Purchase #2	$226.86	12.516%	$255.2538	$255.25	$255.25	$255.30
Purchase #3	$105.53	8.587%	$114.5919	$114.59	$114.60	$114.60
Purchase #4	$183.94	8.308%	$199.2217	$199.22	$199.20	$199.20
Purchase #5	$111.88	13.167%	$126.6112	$126.61	$126.60	$126.60
Purchase #6	$159.74	13.475%	$181.265	$181.27	$181.25	$181.30
Purchase #7	$80.89	12.396%	$90.9171	$90.92	$90.90	$90.90
7 purchase totals =	$1,017.60		$1,121.6696	$1,121.67	$1,121.60	$1,121.70