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	$213.90	11.258%	$237.9809	$237.98	$238.00	$238.00
Purchase #2	$143.86	3.383%	$148.7268	$148.73	$148.75	$148.70
Purchase #3	$83.49	7.447%	$89.7075	$89.71	$89.70	$89.70
Purchase #4	$69.52	4.772%	$72.8375	$72.84	$72.85	$72.80
Purchase #5	$65.28	7.810%	$70.3784	$70.38	$70.40	$70.40
Purchase #6	$51.32	12.844%	$57.9115	$57.91	$57.90	$57.90
Purchase #7	$105.50	10.355%	$116.4245	$116.42	$116.40	$116.40
7 purchase totals =	$732.87		$793.9671	$793.97	$794.00	$793.90