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	$78.53	4.171%	$81.8055	$81.81	$81.80	$81.80
Purchase #2	$42.88	8.171%	$46.3837	$46.38	$46.40	$46.40
Purchase #3	$68.35	4.767%	$71.6082	$71.61	$71.60	$71.60
Purchase #4	$130.29	13.631%	$148.0498	$148.05	$148.05	$148.00
Purchase #5	$237.81	3.553%	$246.2594	$246.26	$246.25	$246.30
Purchase #6	$96.41	3.788%	$100.062	$100.06	$100.05	$100.10
Purchase #7	$131.25	12.867%	$148.1379	$148.14	$148.15	$148.10
7 purchase totals =	$785.52		$842.3065	$842.31	$842.30	$842.30