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	$85.34	10.167%	$94.0165	$94.02	$94.00	$94.00
Purchase #2	$32.72	3.664%	$33.9189	$33.92	$33.90	$33.90
Purchase #3	$54.64	10.348%	$60.2941	$60.29	$60.30	$60.30
Purchase #4	$93.68	9.512%	$102.5908	$102.59	$102.60	$102.60
Purchase #5	$153.72	8.366%	$166.5802	$166.58	$166.60	$166.60
Purchase #6	$153.76	12.309%	$172.6863	$172.69	$172.70	$172.70
Purchase #7	$37.31	9.213%	$40.7474	$40.75	$40.75	$40.70
7 purchase totals =	$611.17		$670.8342	$670.84	$670.85	$670.80