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	$120.47	9.768%	$132.2375	$132.24	$132.25	$132.20
Purchase #2	$91.60	3.498%	$94.8042	$94.80	$94.80	$94.80
Purchase #3	$241.70	7.518%	$259.871	$259.87	$259.85	$259.90
Purchase #4	$20.25	11.578%	$22.5945	$22.59	$22.60	$22.60
Purchase #5	$74.81	4.712%	$78.335	$78.34	$78.35	$78.30
Purchase #6	$181.26	8.230%	$196.1777	$196.18	$196.20	$196.20
Purchase #7	$88.73	3.145%	$91.5206	$91.52	$91.50	$91.50
7 purchase totals =	$818.82		$875.5405	$875.54	$875.55	$875.50