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	$98.61	9.604%	$108.0805	$108.08	$108.10	$108.10
Purchase #2	$234.51	10.830%	$259.9074	$259.91	$259.90	$259.90
Purchase #3	$97.66	3.742%	$101.3144	$101.31	$101.30	$101.30
Purchase #4	$61.46	8.685%	$66.7978	$66.80	$66.80	$66.80
Purchase #5	$180.56	6.309%	$191.9515	$191.95	$191.95	$192.00
Purchase #6	$184.92	11.343%	$205.8955	$205.90	$205.90	$205.90
Purchase #7	$146.68	3.355%	$151.6011	$151.60	$151.60	$151.60
7 purchase totals =	$1,004.40		$1,085.5482	$1,085.55	$1,085.55	$1,085.60