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	$165.66	3.763%	$171.8938	$171.89	$171.90	$171.90
Purchase #2	$21.78	7.383%	$23.388	$23.39	$23.40	$23.40
Purchase #3	$56.93	4.598%	$59.5476	$59.55	$59.55	$59.50
Purchase #4	$66.27	8.405%	$71.84	$71.84	$71.85	$71.80
Purchase #5	$147.77	9.343%	$161.5762	$161.58	$161.60	$161.60
Purchase #6	$108.95	12.723%	$122.8117	$122.81	$122.80	$122.80
Purchase #7	$137.87	3.274%	$142.3839	$142.38	$142.40	$142.40
7 purchase totals =	$705.23		$753.4412	$753.44	$753.50	$753.40