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	$210.68	7.210%	$225.87	$225.87	$225.85	$225.90
Purchase #2	$9.73	13.632%	$11.0564	$11.06	$11.05	$11.10
Purchase #3	$73.91	10.797%	$81.8901	$81.89	$81.90	$81.90
Purchase #4	$237.38	7.693%	$255.6416	$255.64	$255.65	$255.60
Purchase #5	$39.47	3.244%	$40.7504	$40.75	$40.75	$40.80
Purchase #6	$95.72	9.818%	$105.1178	$105.12	$105.10	$105.10
Purchase #7	$68.61	12.719%	$77.3365	$77.34	$77.35	$77.30
7 purchase totals =	$735.50		$797.6628	$797.67	$797.65	$797.70