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	$114.30	10.419%	$126.2089	$126.21	$126.20	$126.20
Purchase #2	$158.78	5.671%	$167.7844	$167.78	$167.80	$167.80
Purchase #3	$67.38	7.259%	$72.2711	$72.27	$72.25	$72.30
Purchase #4	$104.90	9.353%	$114.7113	$114.71	$114.70	$114.70
Purchase #5	$150.56	6.712%	$160.6656	$160.67	$160.65	$160.70
Purchase #6	$67.81	6.149%	$71.9796	$71.98	$72.00	$72.00
Purchase #7	$48.62	4.256%	$50.6893	$50.69	$50.70	$50.70
7 purchase totals =	$712.35		$764.3102	$764.31	$764.30	$764.40