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	$160.61	8.714%	$174.6056	$174.61	$174.60	$174.60
Purchase #2	$29.61	5.175%	$31.1423	$31.14	$31.15	$31.10
Purchase #3	$172.43	13.446%	$195.6149	$195.61	$195.60	$195.60
Purchase #4	$30.50	12.796%	$34.4028	$34.40	$34.40	$34.40
Purchase #5	$139.96	7.800%	$150.8769	$150.88	$150.90	$150.90
Purchase #6	$113.75	12.443%	$127.9039	$127.90	$127.90	$127.90
Purchase #7	$6.75	6.722%	$7.2037	$7.20	$7.20	$7.20
7 purchase totals =	$653.61		$721.7501	$721.74	$721.75	$721.70