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	$10.83	3.162%	$11.1724	$11.17	$11.15	$11.20
Purchase #2	$91.75	9.296%	$100.2791	$100.28	$100.30	$100.30
Purchase #3	$153.99	9.665%	$168.8731	$168.87	$168.85	$168.90
Purchase #4	$174.36	8.443%	$189.0812	$189.08	$189.10	$189.10
Purchase #5	$240.56	10.801%	$266.5429	$266.54	$266.55	$266.50
Purchase #6	$20.55	4.131%	$21.3989	$21.40	$21.40	$21.40
Purchase #7	$240.81	13.276%	$272.7799	$272.78	$272.80	$272.80
7 purchase totals =	$932.85		$1,030.1275	$1,030.12	$1,030.15	$1,030.20