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	$93.45	6.778%	$99.784	$99.78	$99.80	$99.80
Purchase #2	$127.57	4.216%	$132.9484	$132.95	$132.95	$132.90
Purchase #3	$91.60	12.464%	$103.017	$103.02	$103.00	$103.00
Purchase #4	$113.88	9.440%	$124.6303	$124.63	$124.65	$124.60
Purchase #5	$152.31	13.436%	$172.7744	$172.77	$172.75	$172.80
Purchase #6	$195.29	10.515%	$215.8247	$215.82	$215.80	$215.80
Purchase #7	$154.91	3.320%	$160.053	$160.05	$160.05	$160.10
7 purchase totals =	$929.01		$1,009.0318	$1,009.02	$1,009.00	$1,009.00