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	$63.78	3.365%	$65.9262	$65.93	$65.95	$65.90
Purchase #2	$112.77	5.105%	$118.5269	$118.53	$118.55	$118.50
Purchase #3	$147.25	12.560%	$165.7446	$165.74	$165.75	$165.70
Purchase #4	$249.97	13.661%	$284.1184	$284.12	$284.10	$284.10
Purchase #5	$37.30	13.324%	$42.2699	$42.27	$42.25	$42.30
Purchase #6	$40.78	11.524%	$45.4795	$45.48	$45.50	$45.50
Purchase #7	$73.39	4.164%	$76.446	$76.45	$76.45	$76.40
7 purchase totals =	$725.24		$798.5115	$798.52	$798.55	$798.40