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	$185.88	5.775%	$196.6146	$196.61	$196.60	$196.60
Purchase #2	$92.93	7.811%	$100.1888	$100.19	$100.20	$100.20
Purchase #3	$245.94	10.744%	$272.3638	$272.36	$272.35	$272.40
Purchase #4	$173.37	8.685%	$188.4272	$188.43	$188.45	$188.40
Purchase #5	$234.60	13.592%	$266.4868	$266.49	$266.50	$266.50
Purchase #6	$146.43	10.110%	$161.2341	$161.23	$161.25	$161.20
Purchase #7	$142.60	5.390%	$150.2861	$150.29	$150.30	$150.30
7 purchase totals =	$1,221.75		$1,335.6014	$1,335.60	$1,335.65	$1,335.60