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	$62.88	7.866%	$67.8261	$67.83	$67.85	$67.80
Purchase #2	$181.56	4.354%	$189.4651	$189.47	$189.45	$189.50
Purchase #3	$120.73	9.465%	$132.1571	$132.16	$132.15	$132.20
Purchase #4	$141.38	12.147%	$158.5534	$158.55	$158.55	$158.60
Purchase #5	$30.79	4.532%	$32.1854	$32.19	$32.20	$32.20
Purchase #6	$90.62	9.541%	$99.2661	$99.27	$99.25	$99.30
Purchase #7	$48.65	3.347%	$50.2783	$50.28	$50.30	$50.30
7 purchase totals =	$676.61		$729.7315	$729.75	$729.75	$729.90