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	$50.57	8.463%	$54.8497	$54.85	$54.85	$54.80
Purchase #2	$48.78	13.374%	$55.3038	$55.30	$55.30	$55.30
Purchase #3	$29.84	13.457%	$33.8556	$33.86	$33.85	$33.90
Purchase #4	$235.37	8.629%	$255.6801	$255.68	$255.70	$255.70
Purchase #5	$191.80	8.738%	$208.5595	$208.56	$208.55	$208.60
Purchase #6	$166.89	10.353%	$184.1681	$184.17	$184.15	$184.20
Purchase #7	$165.42	4.194%	$172.3577	$172.36	$172.35	$172.40
7 purchase totals =	$888.67		$964.7745	$964.78	$964.75	$964.90