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	$170.68	10.117%	$187.9477	$187.95	$187.95	$187.90
Purchase #2	$128.83	10.631%	$142.5259	$142.53	$142.55	$142.50
Purchase #3	$154.80	6.505%	$164.8697	$164.87	$164.85	$164.90
Purchase #4	$217.94	10.695%	$241.2487	$241.25	$241.25	$241.20
Purchase #5	$9.86	4.429%	$10.2967	$10.30	$10.30	$10.30
Purchase #6	$196.41	10.306%	$216.652	$216.65	$216.65	$216.70
Purchase #7	$81.53	12.348%	$91.5973	$91.60	$91.60	$91.60
7 purchase totals =	$960.05		$1,055.1380	$1,055.15	$1,055.15	$1,055.10