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	$111.40	6.339%	$118.4616	$118.46	$118.45	$118.50
Purchase #2	$125.43	9.658%	$137.544	$137.54	$137.55	$137.50
Purchase #3	$116.83	6.440%	$124.3539	$124.35	$124.35	$124.40
Purchase #4	$155.79	11.249%	$173.3148	$173.31	$173.30	$173.30
Purchase #5	$190.69	11.772%	$213.138	$213.14	$213.15	$213.10
Purchase #6	$189.53	8.226%	$205.1207	$205.12	$205.10	$205.10
Purchase #7	$73.77	13.136%	$83.4604	$83.46	$83.45	$83.50
7 purchase totals =	$963.44		$1,055.3934	$1,055.38	$1,055.35	$1,055.40