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	$83.65	13.577%	$95.0072	$95.01	$95.00	$95.00
Purchase #2	$233.67	6.242%	$248.2557	$248.26	$248.25	$248.30
Purchase #3	$143.92	3.626%	$149.1385	$149.14	$149.15	$149.10
Purchase #4	$20.52	6.675%	$21.8897	$21.89	$21.90	$21.90
Purchase #5	$40.71	13.749%	$46.3072	$46.31	$46.30	$46.30
Purchase #6	$167.66	6.404%	$178.3969	$178.40	$178.40	$178.40
Purchase #7	$91.78	13.648%	$104.3061	$104.31	$104.30	$104.30
7 purchase totals =	$781.91		$843.3013	$843.32	$843.30	$843.30