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	$185.46	5.416%	$195.5045	$195.50	$195.50	$195.50
Purchase #2	$53.29	12.502%	$59.9523	$59.95	$59.95	$60.00
Purchase #3	$164.96	3.365%	$170.5109	$170.51	$170.50	$170.50
Purchase #4	$38.38	13.175%	$43.4366	$43.44	$43.45	$43.40
Purchase #5	$233.45	3.629%	$241.9219	$241.92	$241.90	$241.90
Purchase #6	$240.51	4.409%	$251.1141	$251.11	$251.10	$251.10
Purchase #7	$119.61	7.458%	$128.5305	$128.53	$128.55	$128.50
7 purchase totals =	$1,035.66		$1,090.9708	$1,090.96	$1,090.95	$1,090.90