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	$241.42	8.857%	$262.8026	$262.80	$262.80	$262.80
Purchase #2	$133.89	9.639%	$146.7957	$146.80	$146.80	$146.80
Purchase #3	$12.86	10.261%	$14.1796	$14.18	$14.20	$14.20
Purchase #4	$33.72	6.226%	$35.8194	$35.82	$35.80	$35.80
Purchase #5	$103.69	5.256%	$109.1399	$109.14	$109.15	$109.10
Purchase #6	$33.42	10.764%	$37.0173	$37.02	$37.00	$37.00
Purchase #7	$17.79	11.304%	$19.801	$19.80	$19.80	$19.80
7 purchase totals =	$576.79		$625.5555	$625.56	$625.55	$625.50