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	$181.52	9.292%	$198.3868	$198.39	$198.40	$198.40
Purchase #2	$200.66	8.788%	$218.294	$218.29	$218.30	$218.30
Purchase #3	$41.25	5.736%	$43.6161	$43.62	$43.60	$43.60
Purchase #4	$134.25	5.666%	$141.8566	$141.86	$141.85	$141.90
Purchase #5	$79.49	8.746%	$86.4422	$86.44	$86.45	$86.40
Purchase #6	$221.95	10.142%	$244.4602	$244.46	$244.45	$244.50
Purchase #7	$76.90	11.680%	$85.8819	$85.88	$85.90	$85.90
7 purchase totals =	$936.02		$1,018.9378	$1,018.94	$1,018.95	$1,019.00