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	$23.61	7.637%	$25.4131	$25.41	$25.40	$25.40
Purchase #2	$114.77	7.283%	$123.1287	$123.13	$123.15	$123.10
Purchase #3	$191.57	4.765%	$200.6983	$200.70	$200.70	$200.70
Purchase #4	$45.72	6.324%	$48.6113	$48.61	$48.60	$48.60
Purchase #5	$165.62	13.645%	$188.2188	$188.22	$188.20	$188.20
Purchase #6	$158.67	3.730%	$164.5884	$164.59	$164.60	$164.60
Purchase #7	$111.60	3.848%	$115.8944	$115.89	$115.90	$115.90
7 purchase totals =	$811.56		$866.5530	$866.55	$866.55	$866.50