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	$162.56	5.718%	$171.8552	$171.86	$171.85	$171.90
Purchase #2	$113.78	8.861%	$123.862	$123.86	$123.85	$123.90
Purchase #3	$244.68	13.631%	$278.0323	$278.03	$278.05	$278.00
Purchase #4	$203.54	7.487%	$218.779	$218.78	$218.80	$218.80
Purchase #5	$225.45	5.628%	$238.1383	$238.14	$238.15	$238.10
Purchase #6	$245.93	13.415%	$278.9215	$278.92	$278.90	$278.90
Purchase #7	$203.81	10.745%	$225.7094	$225.71	$225.70	$225.70
7 purchase totals =	$1,399.75		$1,535.2977	$1,535.30	$1,535.30	$1,535.30