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	$83.99	9.462%	$91.9371	$91.94	$91.95	$91.90
Purchase #2	$176.56	12.585%	$198.7801	$198.78	$198.80	$198.80
Purchase #3	$43.38	4.683%	$45.4115	$45.41	$45.40	$45.40
Purchase #4	$89.58	6.311%	$95.2334	$95.23	$95.25	$95.20
Purchase #5	$204.86	3.594%	$212.2227	$212.22	$212.20	$212.20
Purchase #6	$59.36	5.395%	$62.5625	$62.56	$62.55	$62.60
Purchase #7	$55.86	3.721%	$57.9386	$57.94	$57.95	$57.90
7 purchase totals =	$713.59		$764.0859	$764.08	$764.10	$764.00