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	$89.46	7.513%	$96.1811	$96.18	$96.20	$96.20
Purchase #2	$86.66	9.586%	$94.9672	$94.97	$94.95	$95.00
Purchase #3	$75.58	13.259%	$85.6012	$85.60	$85.60	$85.60
Purchase #4	$35.35	12.196%	$39.6613	$39.66	$39.65	$39.70
Purchase #5	$46.61	9.143%	$50.8716	$50.87	$50.85	$50.90
Purchase #6	$48.92	10.754%	$54.1809	$54.18	$54.20	$54.20
Purchase #7	$17.81	11.680%	$19.8902	$19.89	$19.90	$19.90
7 purchase totals =	$400.39		$441.3535	$441.35	$441.35	$441.50