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	$23.92	4.599%	$25.0201	$25.02	$25.00	$25.00
Purchase #2	$196.82	12.274%	$220.9777	$220.98	$221.00	$221.00
Purchase #3	$60.89	8.476%	$66.051	$66.05	$66.05	$66.10
Purchase #4	$147.81	13.191%	$167.3076	$167.31	$167.30	$167.30
Purchase #5	$162.71	5.631%	$171.8722	$171.87	$171.85	$171.90
Purchase #6	$178.69	4.800%	$187.2671	$187.27	$187.25	$187.30
Purchase #7	$43.72	10.815%	$48.4483	$48.45	$48.45	$48.40
7 purchase totals =	$814.56		$886.9440	$886.95	$886.90	$887.00