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	$244.37	11.526%	$272.5361	$272.54	$272.55	$272.50
Purchase #2	$181.89	5.383%	$191.6811	$191.68	$191.70	$191.70
Purchase #3	$110.49	7.209%	$118.4552	$118.46	$118.45	$118.50
Purchase #4	$236.77	3.220%	$244.394	$244.39	$244.40	$244.40
Purchase #5	$77.67	3.236%	$80.1834	$80.18	$80.20	$80.20
Purchase #6	$195.85	7.806%	$211.1381	$211.14	$211.15	$211.10
Purchase #7	$54.25	13.152%	$61.385	$61.39	$61.40	$61.40
7 purchase totals =	$1,101.29		$1,179.7729	$1,179.78	$1,179.85	$1,179.80