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	$44.36	9.170%	$48.4278	$48.43	$48.45	$48.40
Purchase #2	$109.37	3.794%	$113.5195	$113.52	$113.50	$113.50
Purchase #3	$211.55	3.460%	$218.8696	$218.87	$218.85	$218.90
Purchase #4	$59.50	13.514%	$67.5408	$67.54	$67.55	$67.50
Purchase #5	$150.75	10.475%	$166.5411	$166.54	$166.55	$166.50
Purchase #6	$55.95	6.186%	$59.4111	$59.41	$59.40	$59.40
Purchase #7	$225.74	5.797%	$238.8261	$238.83	$238.85	$238.80
7 purchase totals =	$857.22		$913.1360	$913.14	$913.15	$913.00