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	$133.74	3.118%	$137.91	$137.91	$137.90	$137.90
Purchase #2	$204.29	12.564%	$229.957	$229.96	$229.95	$230.00
Purchase #3	$206.61	7.796%	$222.7173	$222.72	$222.70	$222.70
Purchase #4	$237.78	13.484%	$269.8423	$269.84	$269.85	$269.80
Purchase #5	$49.50	7.185%	$53.0566	$53.06	$53.05	$53.10
Purchase #6	$203.62	4.409%	$212.5976	$212.60	$212.60	$212.60
Purchase #7	$52.85	13.161%	$59.8056	$59.81	$59.80	$59.80
7 purchase totals =	$1,088.39		$1,185.8864	$1,185.90	$1,185.85	$1,185.90