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	$145.28	9.190%	$158.6312	$158.63	$158.65	$158.60
Purchase #2	$96.63	13.442%	$109.619	$109.62	$109.60	$109.60
Purchase #3	$85.85	3.431%	$88.7955	$88.80	$88.80	$88.80
Purchase #4	$31.64	7.619%	$34.0507	$34.05	$34.05	$34.10
Purchase #5	$99.82	4.493%	$104.3049	$104.30	$104.30	$104.30
Purchase #6	$162.60	3.485%	$168.2666	$168.27	$168.25	$168.30
Purchase #7	$91.67	8.286%	$99.2658	$99.27	$99.25	$99.30
7 purchase totals =	$713.49		$762.9337	$762.94	$762.90	$763.00