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	$29.91	6.765%	$31.9334	$31.93	$31.95	$31.90
Purchase #2	$90.77	13.621%	$103.1338	$103.13	$103.15	$103.10
Purchase #3	$171.27	10.131%	$188.6214	$188.62	$188.60	$188.60
Purchase #4	$51.30	10.631%	$56.7537	$56.75	$56.75	$56.80
Purchase #5	$167.51	8.133%	$181.1336	$181.13	$181.15	$181.10
Purchase #6	$45.29	3.249%	$46.7615	$46.76	$46.75	$46.80
Purchase #7	$148.66	10.588%	$164.4001	$164.40	$164.40	$164.40
7 purchase totals =	$704.71		$772.7375	$772.72	$772.75	$772.70