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	$14.37	13.516%	$16.3122	$16.31	$16.30	$16.30
Purchase #2	$127.93	4.723%	$133.9721	$133.97	$133.95	$134.00
Purchase #3	$187.74	4.687%	$196.5394	$196.54	$196.55	$196.50
Purchase #4	$216.79	11.761%	$242.2867	$242.29	$242.30	$242.30
Purchase #5	$73.45	12.514%	$82.6415	$82.64	$82.65	$82.60
Purchase #6	$116.45	13.183%	$131.8016	$131.80	$131.80	$131.80
Purchase #7	$110.82	13.776%	$126.0866	$126.09	$126.10	$126.10
7 purchase totals =	$847.55		$929.6401	$929.64	$929.65	$929.60