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	$176.44	7.687%	$190.0029	$190.00	$190.00	$190.00
Purchase #2	$109.30	8.451%	$118.5369	$118.54	$118.55	$118.50
Purchase #3	$151.77	4.682%	$158.8759	$158.88	$158.90	$158.90
Purchase #4	$244.57	5.548%	$258.1387	$258.14	$258.15	$258.10
Purchase #5	$42.32	5.528%	$44.6594	$44.66	$44.65	$44.70
Purchase #6	$85.43	4.677%	$89.4256	$89.43	$89.45	$89.40
Purchase #7	$249.43	5.334%	$262.7346	$262.73	$262.75	$262.70
7 purchase totals =	$1,059.26		$1,122.3740	$1,122.38	$1,122.45	$1,122.30