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	$136.92	11.611%	$152.8178	$152.82	$152.80	$152.80
Purchase #2	$90.36	13.594%	$102.6435	$102.64	$102.65	$102.60
Purchase #3	$126.77	3.444%	$131.136	$131.14	$131.15	$131.10
Purchase #4	$138.99	9.498%	$152.1913	$152.19	$152.20	$152.20
Purchase #5	$64.71	5.376%	$68.1888	$68.19	$68.20	$68.20
Purchase #6	$129.81	7.768%	$139.8936	$139.89	$139.90	$139.90
Purchase #7	$246.29	10.318%	$271.7022	$271.70	$271.70	$271.70
7 purchase totals =	$933.85		$1,018.5732	$1,018.57	$1,018.60	$1,018.50