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	$34.46	3.470%	$35.6558	$35.66	$35.65	$35.70
Purchase #2	$11.76	6.108%	$12.4783	$12.48	$12.50	$12.50
Purchase #3	$81.59	4.455%	$85.2248	$85.22	$85.20	$85.20
Purchase #4	$76.33	6.476%	$81.2731	$81.27	$81.25	$81.30
Purchase #5	$138.66	3.320%	$143.2635	$143.26	$143.25	$143.30
Purchase #6	$162.31	3.267%	$167.6127	$167.61	$167.60	$167.60
Purchase #7	$62.54	8.651%	$67.9503	$67.95	$67.95	$68.00
7 purchase totals =	$567.65		$593.4585	$593.45	$593.40	$593.60