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	$64.88	3.403%	$67.0879	$67.09	$67.10	$67.10
Purchase #2	$60.51	5.661%	$63.9355	$63.94	$63.95	$63.90
Purchase #3	$24.49	5.632%	$25.8693	$25.87	$25.85	$25.90
Purchase #4	$38.63	8.390%	$41.8711	$41.87	$41.85	$41.90
Purchase #5	$137.60	11.634%	$153.6084	$153.61	$153.60	$153.60
Purchase #6	$29.41	8.736%	$31.9793	$31.98	$32.00	$32.00
Purchase #7	$250.41	7.478%	$269.1357	$269.14	$269.15	$269.10
7 purchase totals =	$605.93		$653.4872	$653.50	$653.50	$653.50