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	$55.56	10.425%	$61.3521	$61.35	$61.35	$61.40
Purchase #2	$214.80	7.350%	$230.5878	$230.59	$230.60	$230.60
Purchase #3	$37.67	7.426%	$40.4674	$40.47	$40.45	$40.50
Purchase #4	$53.86	5.213%	$56.6677	$56.67	$56.65	$56.70
Purchase #5	$89.84	7.745%	$96.7981	$96.80	$96.80	$96.80
Purchase #6	$248.25	13.150%	$280.8949	$280.89	$280.90	$280.90
Purchase #7	$82.64	13.561%	$93.8468	$93.85	$93.85	$93.80
7 purchase totals =	$782.62		$860.6148	$860.62	$860.60	$860.70