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	$160.32	7.509%	$172.3584	$172.36	$172.35	$172.40
Purchase #2	$160.29	7.337%	$172.0505	$172.05	$172.05	$172.10
Purchase #3	$122.37	5.168%	$128.6941	$128.69	$128.70	$128.70
Purchase #4	$114.95	5.180%	$120.9044	$120.90	$120.90	$120.90
Purchase #5	$179.53	3.380%	$185.5981	$185.60	$185.60	$185.60
Purchase #6	$147.28	9.287%	$160.9579	$160.96	$160.95	$161.00
Purchase #7	$183.31	11.247%	$203.9269	$203.93	$203.95	$203.90
7 purchase totals =	$1,068.05		$1,144.4903	$1,144.49	$1,144.50	$1,144.60