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	$124.75	11.436%	$139.0164	$139.02	$139.00	$139.00
Purchase #2	$226.77	9.287%	$247.8301	$247.83	$247.85	$247.80
Purchase #3	$141.54	12.335%	$158.999	$159.00	$159.00	$159.00
Purchase #4	$89.59	11.386%	$99.7907	$99.79	$99.80	$99.80
Purchase #5	$219.42	13.845%	$249.7987	$249.80	$249.80	$249.80
Purchase #6	$151.82	13.476%	$172.2793	$172.28	$172.30	$172.30
Purchase #7	$84.60	11.492%	$94.3222	$94.32	$94.30	$94.30
7 purchase totals =	$1,038.49		$1,162.0364	$1,162.04	$1,162.05	$1,162.00