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	$156.27	10.414%	$172.544	$172.54	$172.55	$172.50
Purchase #2	$114.97	9.497%	$125.8887	$125.89	$125.90	$125.90
Purchase #3	$168.55	9.842%	$185.1387	$185.14	$185.15	$185.10
Purchase #4	$118.28	6.477%	$125.941	$125.94	$125.95	$125.90
Purchase #5	$109.70	3.563%	$113.6086	$113.61	$113.60	$113.60
Purchase #6	$241.81	5.729%	$255.6633	$255.66	$255.65	$255.70
Purchase #7	$95.62	9.620%	$104.8186	$104.82	$104.80	$104.80
7 purchase totals =	$1,005.20		$1,083.6029	$1,083.60	$1,083.60	$1,083.50