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	$66.91	10.711%	$74.0767	$74.08	$74.10	$74.10
Purchase #2	$142.50	13.124%	$161.2017	$161.20	$161.20	$161.20
Purchase #3	$150.66	5.272%	$158.6028	$158.60	$158.60	$158.60
Purchase #4	$31.27	13.752%	$35.5703	$35.57	$35.55	$35.60
Purchase #5	$236.81	11.691%	$264.4955	$264.50	$264.50	$264.50
Purchase #6	$196.93	9.839%	$216.3059	$216.31	$216.30	$216.30
Purchase #7	$57.48	3.594%	$59.5458	$59.55	$59.55	$59.50
7 purchase totals =	$882.56		$969.7987	$969.81	$969.80	$969.80