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	$158.52	12.268%	$177.9672	$177.97	$177.95	$178.00
Purchase #2	$246.80	13.635%	$280.4512	$280.45	$280.45	$280.50
Purchase #3	$122.73	4.418%	$128.1522	$128.15	$128.15	$128.20
Purchase #4	$59.34	11.235%	$66.0068	$66.01	$66.00	$66.00
Purchase #5	$162.53	13.449%	$184.3887	$184.39	$184.40	$184.40
Purchase #6	$31.58	12.429%	$35.5051	$35.51	$35.50	$35.50
Purchase #7	$239.70	13.428%	$271.8869	$271.89	$271.90	$271.90
7 purchase totals =	$1,021.20		$1,144.3581	$1,144.37	$1,144.35	$1,144.50