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	$231.94	10.145%	$255.4703	$255.47	$255.45	$255.50
Purchase #2	$28.40	5.145%	$29.8612	$29.86	$29.85	$29.90
Purchase #3	$93.49	6.575%	$99.637	$99.64	$99.65	$99.60
Purchase #4	$238.77	13.428%	$270.832	$270.83	$270.85	$270.80
Purchase #5	$93.93	9.715%	$103.0553	$103.06	$103.05	$103.10
Purchase #6	$104.97	4.435%	$109.6254	$109.63	$109.65	$109.60
Purchase #7	$82.40	11.595%	$91.9543	$91.95	$91.95	$92.00
7 purchase totals =	$873.90		$960.4355	$960.44	$960.45	$960.50