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	$151.90	4.319%	$158.4606	$158.46	$158.45	$158.50
Purchase #2	$248.33	13.702%	$282.3562	$282.36	$282.35	$282.40
Purchase #3	$89.51	11.426%	$99.7374	$99.74	$99.75	$99.70
Purchase #4	$59.57	6.371%	$63.3652	$63.37	$63.35	$63.40
Purchase #5	$58.57	5.214%	$61.6238	$61.62	$61.60	$61.60
Purchase #6	$44.64	4.583%	$46.6859	$46.69	$46.70	$46.70
Purchase #7	$14.46	5.281%	$15.2236	$15.22	$15.20	$15.20
7 purchase totals =	$666.98		$727.4527	$727.46	$727.40	$727.50