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	$29.33	8.234%	$31.745	$31.75	$31.75	$31.70
Purchase #2	$87.32	3.571%	$90.4382	$90.44	$90.45	$90.40
Purchase #3	$199.46	13.241%	$225.8705	$225.87	$225.85	$225.90
Purchase #4	$209.49	13.815%	$238.431	$238.43	$238.45	$238.40
Purchase #5	$44.91	8.806%	$48.8648	$48.86	$48.85	$48.90
Purchase #6	$167.42	7.157%	$179.4022	$179.40	$179.40	$179.40
Purchase #7	$73.55	5.650%	$77.7056	$77.71	$77.70	$77.70
7 purchase totals =	$811.48		$892.4573	$892.46	$892.45	$892.40