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	$96.47	7.539%	$103.7429	$103.74	$103.75	$103.70
Purchase #2	$187.92	12.796%	$211.9662	$211.97	$211.95	$212.00
Purchase #3	$145.95	6.784%	$155.8512	$155.85	$155.85	$155.90
Purchase #4	$169.82	9.253%	$185.5334	$185.53	$185.55	$185.50
Purchase #5	$113.41	11.250%	$126.1686	$126.17	$126.15	$126.20
Purchase #6	$133.52	8.839%	$145.3218	$145.32	$145.30	$145.30
Purchase #7	$13.40	11.483%	$14.9387	$14.94	$14.95	$14.90
7 purchase totals =	$860.49		$943.5228	$943.52	$943.50	$943.50