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	$169.37	10.212%	$186.6661	$186.67	$186.65	$186.70
Purchase #2	$218.77	7.244%	$234.6177	$234.62	$234.60	$234.60
Purchase #3	$224.35	6.729%	$239.4465	$239.45	$239.45	$239.40
Purchase #4	$53.62	8.724%	$58.2978	$58.30	$58.30	$58.30
Purchase #5	$216.52	4.314%	$225.8607	$225.86	$225.85	$225.90
Purchase #6	$148.30	10.631%	$164.0658	$164.07	$164.05	$164.10
Purchase #7	$185.31	3.292%	$191.4104	$191.41	$191.40	$191.40
7 purchase totals =	$1,216.24		$1,300.3650	$1,300.38	$1,300.30	$1,300.40