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	$196.51	8.685%	$213.5769	$213.58	$213.60	$213.60
Purchase #2	$39.60	13.176%	$44.8177	$44.82	$44.80	$44.80
Purchase #3	$31.30	10.344%	$34.5377	$34.54	$34.55	$34.50
Purchase #4	$135.69	13.198%	$153.5984	$153.60	$153.60	$153.60
Purchase #5	$207.52	10.601%	$229.5192	$229.52	$229.50	$229.50
Purchase #6	$109.41	8.280%	$118.4691	$118.47	$118.45	$118.50
Purchase #7	$210.98	5.861%	$223.3455	$223.35	$223.35	$223.30
7 purchase totals =	$931.01		$1,017.8645	$1,017.88	$1,017.85	$1,017.80