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	$38.71	11.346%	$43.102	$43.10	$43.10	$43.10
Purchase #2	$70.96	8.273%	$76.8305	$76.83	$76.85	$76.80
Purchase #3	$214.54	5.756%	$226.8889	$226.89	$226.90	$226.90
Purchase #4	$196.27	13.299%	$222.3719	$222.37	$222.35	$222.40
Purchase #5	$191.72	10.730%	$212.2916	$212.29	$212.30	$212.30
Purchase #6	$25.58	5.336%	$26.9449	$26.94	$26.95	$26.90
Purchase #7	$67.70	6.395%	$72.0294	$72.03	$72.05	$72.00
7 purchase totals =	$805.48		$880.4592	$880.45	$880.50	$880.40