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	$106.93	6.265%	$113.6292	$113.63	$113.65	$113.60
Purchase #2	$199.52	6.691%	$212.8699	$212.87	$212.85	$212.90
Purchase #3	$74.43	11.147%	$82.7267	$82.73	$82.75	$82.70
Purchase #4	$185.61	5.716%	$196.2195	$196.22	$196.20	$196.20
Purchase #5	$190.85	12.635%	$214.9639	$214.96	$214.95	$215.00
Purchase #6	$103.94	5.216%	$109.3615	$109.36	$109.35	$109.40
Purchase #7	$225.74	11.831%	$252.4473	$252.45	$252.45	$252.40
7 purchase totals =	$1,087.02		$1,182.2180	$1,182.22	$1,182.20	$1,182.20