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	$212.87	11.210%	$236.7327	$236.73	$236.75	$236.70
Purchase #2	$227.75	13.286%	$258.0089	$258.01	$258.00	$258.00
Purchase #3	$44.85	11.342%	$49.9369	$49.94	$49.95	$49.90
Purchase #4	$43.80	4.849%	$45.9239	$45.92	$45.90	$45.90
Purchase #5	$142.94	6.663%	$152.4641	$152.46	$152.45	$152.50
Purchase #6	$105.46	9.517%	$115.4966	$115.50	$115.50	$115.50
Purchase #7	$171.56	5.532%	$181.0507	$181.05	$181.05	$181.10
7 purchase totals =	$949.23		$1,039.6138	$1,039.61	$1,039.60	$1,039.60