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	$22.55	13.531%	$25.6012	$25.60	$25.60	$25.60
Purchase #2	$84.51	3.492%	$87.4611	$87.46	$87.45	$87.50
Purchase #3	$49.99	3.401%	$51.6902	$51.69	$51.70	$51.70
Purchase #4	$39.91	13.326%	$45.2284	$45.23	$45.25	$45.20
Purchase #5	$241.32	5.512%	$254.6216	$254.62	$254.60	$254.60
Purchase #6	$85.64	6.153%	$90.9094	$90.91	$90.90	$90.90
Purchase #7	$169.96	11.263%	$189.1026	$189.10	$189.10	$189.10
7 purchase totals =	$693.88		$744.6145	$744.61	$744.60	$744.60