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	$244.83	3.662%	$253.7957	$253.80	$253.80	$253.80
Purchase #2	$115.27	7.834%	$124.3003	$124.30	$124.30	$124.30
Purchase #3	$172.97	7.443%	$185.8442	$185.84	$185.85	$185.80
Purchase #4	$77.66	11.501%	$86.5917	$86.59	$86.60	$86.60
Purchase #5	$48.84	6.152%	$51.8446	$51.84	$51.85	$51.80
Purchase #6	$138.55	12.643%	$156.0669	$156.07	$156.05	$156.10
Purchase #7	$171.89	10.176%	$189.3815	$189.38	$189.40	$189.40
7 purchase totals =	$970.01		$1,047.8249	$1,047.82	$1,047.85	$1,047.80