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	$103.92	11.128%	$115.4842	$115.48	$115.50	$115.50
Purchase #2	$195.32	13.562%	$221.8093	$221.81	$221.80	$221.80
Purchase #3	$233.38	5.382%	$245.9405	$245.94	$245.95	$245.90
Purchase #4	$53.89	11.410%	$60.0388	$60.04	$60.05	$60.00
Purchase #5	$19.54	5.190%	$20.5541	$20.55	$20.55	$20.60
Purchase #6	$165.45	6.388%	$176.0189	$176.02	$176.00	$176.00
Purchase #7	$40.26	5.269%	$42.3813	$42.38	$42.40	$42.40
7 purchase totals =	$811.76		$882.2271	$882.22	$882.25	$882.20