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	$109.41	5.431%	$115.3521	$115.35	$115.35	$115.40
Purchase #2	$75.47	13.775%	$85.866	$85.87	$85.85	$85.90
Purchase #3	$56.88	9.578%	$62.328	$62.33	$62.35	$62.30
Purchase #4	$94.98	4.693%	$99.4374	$99.44	$99.45	$99.40
Purchase #5	$128.93	6.601%	$137.4407	$137.44	$137.45	$137.40
Purchase #6	$204.31	3.400%	$211.2565	$211.26	$211.25	$211.30
Purchase #7	$111.31	13.731%	$126.594	$126.59	$126.60	$126.60
7 purchase totals =	$781.29		$838.2747	$838.28	$838.30	$838.30