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	$127.55	4.742%	$133.5984	$133.60	$133.60	$133.60
Purchase #2	$10.35	12.402%	$11.6336	$11.63	$11.65	$11.60
Purchase #3	$40.75	12.521%	$45.8523	$45.85	$45.85	$45.90
Purchase #4	$144.82	4.864%	$151.864	$151.86	$151.85	$151.90
Purchase #5	$174.58	8.762%	$189.8767	$189.88	$189.90	$189.90
Purchase #6	$54.99	7.552%	$59.1428	$59.14	$59.15	$59.10
Purchase #7	$87.57	3.569%	$90.6954	$90.70	$90.70	$90.70
7 purchase totals =	$640.61		$682.6632	$682.66	$682.70	$682.70