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	$86.83	11.509%	$96.8233	$96.82	$96.80	$96.80
Purchase #2	$239.75	7.128%	$256.8394	$256.84	$256.85	$256.80
Purchase #3	$207.36	4.218%	$216.1064	$216.11	$216.10	$216.10
Purchase #4	$233.34	8.692%	$253.6219	$253.62	$253.60	$253.60
Purchase #5	$198.65	13.707%	$225.879	$225.88	$225.90	$225.90
Purchase #6	$35.86	3.287%	$37.0387	$37.04	$37.05	$37.00
Purchase #7	$83.99	6.657%	$89.5812	$89.58	$89.60	$89.60
7 purchase totals =	$1,085.78		$1,175.8899	$1,175.89	$1,175.90	$1,175.80