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	$198.94	11.706%	$222.2279	$222.23	$222.25	$222.20
Purchase #2	$144.95	5.417%	$152.8019	$152.80	$152.80	$152.80
Purchase #3	$239.68	3.406%	$247.8435	$247.84	$247.85	$247.80
Purchase #4	$161.83	11.601%	$180.6039	$180.60	$180.60	$180.60
Purchase #5	$140.69	10.561%	$155.5483	$155.55	$155.55	$155.50
Purchase #6	$43.62	3.212%	$45.0211	$45.02	$45.00	$45.00
Purchase #7	$37.76	6.854%	$40.3481	$40.35	$40.35	$40.30
7 purchase totals =	$967.47		$1,044.3947	$1,044.39	$1,044.40	$1,044.20