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	$205.67	10.479%	$227.2222	$227.22	$227.20	$227.20
Purchase #2	$213.35	12.713%	$240.4732	$240.47	$240.45	$240.50
Purchase #3	$212.84	13.340%	$241.2329	$241.23	$241.25	$241.20
Purchase #4	$70.56	10.753%	$78.1473	$78.15	$78.15	$78.10
Purchase #5	$54.41	6.451%	$57.92	$57.92	$57.90	$57.90
Purchase #6	$66.60	11.386%	$74.1831	$74.18	$74.20	$74.20
Purchase #7	$155.37	11.582%	$173.365	$173.37	$173.35	$173.40
7 purchase totals =	$978.80		$1,092.5437	$1,092.54	$1,092.50	$1,092.50