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	$151.62	9.690%	$166.312	$166.31	$166.30	$166.30
Purchase #2	$83.78	5.771%	$88.6149	$88.61	$88.60	$88.60
Purchase #3	$137.89	10.547%	$152.4333	$152.43	$152.45	$152.40
Purchase #4	$120.94	4.107%	$125.907	$125.91	$125.90	$125.90
Purchase #5	$82.95	3.197%	$85.6019	$85.60	$85.60	$85.60
Purchase #6	$53.65	3.536%	$55.5471	$55.55	$55.55	$55.50
Purchase #7	$63.94	4.238%	$66.6498	$66.65	$66.65	$66.60
7 purchase totals =	$694.77		$741.0660	$741.06	$741.05	$740.90