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	$39.63	3.340%	$40.9536	$40.95	$40.95	$41.00
Purchase #2	$119.53	7.707%	$128.7422	$128.74	$128.75	$128.70
Purchase #3	$75.73	7.797%	$81.6347	$81.63	$81.65	$81.60
Purchase #4	$62.72	13.636%	$71.2725	$71.27	$71.25	$71.30
Purchase #5	$179.84	10.174%	$198.1369	$198.14	$198.15	$198.10
Purchase #6	$208.75	8.783%	$227.0845	$227.08	$227.10	$227.10
Purchase #7	$56.45	6.142%	$59.9172	$59.92	$59.90	$59.90
7 purchase totals =	$742.65		$807.7416	$807.73	$807.75	$807.70