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	$81.56	4.561%	$85.28	$85.28	$85.30	$85.30
Purchase #2	$35.67	10.227%	$39.318	$39.32	$39.30	$39.30
Purchase #3	$202.63	7.707%	$218.2467	$218.25	$218.25	$218.20
Purchase #4	$43.71	4.848%	$45.8291	$45.83	$45.85	$45.80
Purchase #5	$58.77	13.763%	$66.8585	$66.86	$66.85	$66.90
Purchase #6	$67.49	11.339%	$75.1427	$75.14	$75.15	$75.10
Purchase #7	$167.92	10.721%	$185.9227	$185.92	$185.90	$185.90
7 purchase totals =	$657.75		$716.5977	$716.60	$716.60	$716.50