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	$61.77	11.721%	$69.0101	$69.01	$69.00	$69.00
Purchase #2	$102.89	6.203%	$109.2723	$109.27	$109.25	$109.30
Purchase #3	$112.30	13.392%	$127.3392	$127.34	$127.35	$127.30
Purchase #4	$13.86	13.612%	$15.7466	$15.75	$15.75	$15.70
Purchase #5	$118.91	13.188%	$134.5919	$134.59	$134.60	$134.60
Purchase #6	$227.67	11.554%	$253.975	$253.98	$254.00	$254.00
Purchase #7	$134.78	4.869%	$141.3424	$141.34	$141.35	$141.30
7 purchase totals =	$772.18		$851.2775	$851.28	$851.30	$851.20