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	$204.86	6.770%	$218.729	$218.73	$218.75	$218.70
Purchase #2	$154.82	11.510%	$172.6398	$172.64	$172.65	$172.60
Purchase #3	$92.38	10.499%	$102.079	$102.08	$102.10	$102.10
Purchase #4	$67.74	6.509%	$72.1492	$72.15	$72.15	$72.10
Purchase #5	$192.83	6.347%	$205.0689	$205.07	$205.05	$205.10
Purchase #6	$68.38	3.384%	$70.694	$70.69	$70.70	$70.70
Purchase #7	$109.61	12.821%	$123.6631	$123.66	$123.65	$123.70
7 purchase totals =	$890.62		$965.0230	$965.02	$965.05	$965.00