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	$141.55	4.871%	$148.4449	$148.44	$148.45	$148.40
Purchase #2	$50.46	3.814%	$52.3845	$52.38	$52.40	$52.40
Purchase #3	$149.90	5.758%	$158.5312	$158.53	$158.55	$158.50
Purchase #4	$19.82	11.847%	$22.1681	$22.17	$22.15	$22.20
Purchase #5	$51.48	3.675%	$53.3719	$53.37	$53.35	$53.40
Purchase #6	$83.58	9.558%	$91.5686	$91.57	$91.55	$91.60
Purchase #7	$35.85	13.828%	$40.8073	$40.81	$40.80	$40.80
7 purchase totals =	$532.64		$567.2765	$567.27	$567.25	$567.30