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	$101.74	7.557%	$109.4285	$109.43	$109.45	$109.40
Purchase #2	$35.79	11.303%	$39.8353	$39.84	$39.85	$39.80
Purchase #3	$59.84	3.277%	$61.801	$61.80	$61.80	$61.80
Purchase #4	$20.52	11.490%	$22.8777	$22.88	$22.90	$22.90
Purchase #5	$100.76	5.179%	$105.9784	$105.98	$106.00	$106.00
Purchase #6	$58.98	8.639%	$64.0753	$64.08	$64.10	$64.10
Purchase #7	$225.87	9.119%	$246.4671	$246.47	$246.45	$246.50
7 purchase totals =	$603.50		$650.4633	$650.48	$650.55	$650.50