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	$212.71	4.571%	$222.433	$222.43	$222.45	$222.40
Purchase #2	$178.86	3.597%	$185.2936	$185.29	$185.30	$185.30
Purchase #3	$188.43	4.189%	$196.3233	$196.32	$196.30	$196.30
Purchase #4	$63.82	11.599%	$71.2225	$71.22	$71.20	$71.20
Purchase #5	$239.65	10.412%	$264.6024	$264.60	$264.60	$264.60
Purchase #6	$223.47	7.873%	$241.0638	$241.06	$241.05	$241.10
Purchase #7	$72.65	5.658%	$76.7605	$76.76	$76.75	$76.80
7 purchase totals =	$1,179.59		$1,257.6991	$1,257.68	$1,257.65	$1,257.70