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	$187.91	12.639%	$211.6599	$211.66	$211.65	$211.70
Purchase #2	$66.76	6.675%	$71.2162	$71.22	$71.20	$71.20
Purchase #3	$36.31	13.840%	$41.3353	$41.34	$41.35	$41.30
Purchase #4	$89.35	13.545%	$101.4525	$101.45	$101.45	$101.50
Purchase #5	$46.95	3.296%	$48.4975	$48.50	$48.50	$48.50
Purchase #6	$76.75	11.760%	$85.7758	$85.78	$85.80	$85.80
Purchase #7	$49.71	13.699%	$56.5198	$56.52	$56.50	$56.50
7 purchase totals =	$553.74		$616.4570	$616.47	$616.45	$616.50