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	$100.30	9.519%	$109.8476	$109.85	$109.85	$109.80
Purchase #2	$50.59	12.181%	$56.7524	$56.75	$56.75	$56.80
Purchase #3	$28.91	3.207%	$29.8371	$29.84	$29.85	$29.80
Purchase #4	$204.35	5.122%	$214.8168	$214.82	$214.80	$214.80
Purchase #5	$70.61	10.689%	$78.1575	$78.16	$78.15	$78.20
Purchase #6	$179.63	3.477%	$185.8757	$185.88	$185.90	$185.90
Purchase #7	$46.35	11.207%	$51.5444	$51.54	$51.55	$51.50
7 purchase totals =	$680.74		$726.8315	$726.84	$726.85	$726.80