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	$67.29	6.195%	$71.4586	$71.46	$71.45	$71.50
Purchase #2	$216.70	6.796%	$231.4269	$231.43	$231.45	$231.40
Purchase #3	$42.44	13.837%	$48.3124	$48.31	$48.30	$48.30
Purchase #4	$98.30	12.788%	$110.8706	$110.87	$110.85	$110.90
Purchase #5	$9.64	7.855%	$10.3972	$10.40	$10.40	$10.40
Purchase #6	$18.43	5.589%	$19.4601	$19.46	$19.45	$19.50
Purchase #7	$232.94	3.224%	$240.45	$240.45	$240.45	$240.50
7 purchase totals =	$685.74		$732.3758	$732.38	$732.35	$732.50