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	$241.80	10.667%	$267.5928	$267.59	$267.60	$267.60
Purchase #2	$184.32	6.195%	$195.7386	$195.74	$195.75	$195.70
Purchase #3	$23.40	3.234%	$24.1568	$24.16	$24.15	$24.20
Purchase #4	$177.34	10.764%	$196.4289	$196.43	$196.45	$196.40
Purchase #5	$117.75	7.504%	$126.586	$126.59	$126.60	$126.60
Purchase #6	$123.69	10.321%	$136.456	$136.46	$136.45	$136.50
Purchase #7	$111.44	3.148%	$114.9481	$114.95	$114.95	$114.90
7 purchase totals =	$979.74		$1,061.9072	$1,061.92	$1,061.95	$1,061.90