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	$199.87	11.447%	$222.7491	$222.75	$222.75	$222.70
Purchase #2	$137.94	9.200%	$150.6305	$150.63	$150.65	$150.60
Purchase #3	$151.49	13.191%	$171.473	$171.47	$171.45	$171.50
Purchase #4	$26.66	13.253%	$30.1932	$30.19	$30.20	$30.20
Purchase #5	$39.76	5.378%	$41.8983	$41.90	$41.90	$41.90
Purchase #6	$39.62	4.680%	$41.4742	$41.47	$41.45	$41.50
Purchase #7	$105.37	7.680%	$113.4624	$113.46	$113.45	$113.50
7 purchase totals =	$700.71		$771.8807	$771.87	$771.85	$771.90