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	$184.39	11.852%	$206.2439	$206.24	$206.25	$206.20
Purchase #2	$131.70	11.282%	$146.5584	$146.56	$146.55	$146.60
Purchase #3	$144.55	5.774%	$152.8963	$152.90	$152.90	$152.90
Purchase #4	$41.49	12.754%	$46.7816	$46.78	$46.80	$46.80
Purchase #5	$156.97	9.763%	$172.295	$172.30	$172.30	$172.30
Purchase #6	$169.25	3.124%	$174.5374	$174.54	$174.55	$174.50
Purchase #7	$50.93	5.313%	$53.6359	$53.64	$53.65	$53.60
7 purchase totals =	$879.28		$952.9485	$952.96	$953.00	$952.90