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	$196.51	11.328%	$218.7707	$218.77	$218.75	$218.80
Purchase #2	$57.48	13.602%	$65.2984	$65.30	$65.30	$65.30
Purchase #3	$99.96	12.381%	$112.336	$112.34	$112.35	$112.30
Purchase #4	$18.81	8.386%	$20.3874	$20.39	$20.40	$20.40
Purchase #5	$43.42	5.293%	$45.7182	$45.72	$45.70	$45.70
Purchase #6	$244.78	6.508%	$260.7103	$260.71	$260.70	$260.70
Purchase #7	$205.74	12.489%	$231.4349	$231.43	$231.45	$231.40
7 purchase totals =	$866.70		$954.6559	$954.66	$954.65	$954.60