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	$89.31	12.664%	$100.6202	$100.62	$100.60	$100.60
Purchase #2	$163.42	13.489%	$185.4637	$185.46	$185.45	$185.50
Purchase #3	$9.81	12.652%	$11.0512	$11.05	$11.05	$11.10
Purchase #4	$213.88	5.696%	$226.0626	$226.06	$226.05	$226.10
Purchase #5	$151.39	5.824%	$160.207	$160.21	$160.20	$160.20
Purchase #6	$99.96	13.133%	$113.0877	$113.09	$113.10	$113.10
Purchase #7	$28.60	4.627%	$29.9233	$29.92	$29.90	$29.90
7 purchase totals =	$756.37		$826.4157	$826.41	$826.35	$826.50