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	$105.54	5.558%	$111.4059	$111.41	$111.40	$111.40
Purchase #2	$55.71	7.347%	$59.803	$59.80	$59.80	$59.80
Purchase #3	$131.82	11.292%	$146.7051	$146.71	$146.70	$146.70
Purchase #4	$221.79	12.382%	$249.252	$249.25	$249.25	$249.30
Purchase #5	$49.75	10.749%	$55.0976	$55.10	$55.10	$55.10
Purchase #6	$96.47	13.139%	$109.1452	$109.15	$109.15	$109.10
Purchase #7	$66.93	12.723%	$75.4455	$75.45	$75.45	$75.40
7 purchase totals =	$728.01		$806.8543	$806.87	$806.85	$806.80