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	$166.57	11.117%	$185.0876	$185.09	$185.10	$185.10
Purchase #2	$123.39	6.834%	$131.8225	$131.82	$131.80	$131.80
Purchase #3	$216.30	6.758%	$230.9176	$230.92	$230.90	$230.90
Purchase #4	$234.51	11.430%	$261.3145	$261.31	$261.30	$261.30
Purchase #5	$18.85	10.546%	$20.8379	$20.84	$20.85	$20.80
Purchase #6	$210.39	5.803%	$222.5989	$222.60	$222.60	$222.60
Purchase #7	$86.46	5.191%	$90.9481	$90.95	$90.95	$90.90
7 purchase totals =	$1,056.47		$1,143.5271	$1,143.53	$1,143.50	$1,143.40