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	$128.65	4.191%	$134.0417	$134.04	$134.05	$134.00
Purchase #2	$231.58	7.426%	$248.7771	$248.78	$248.80	$248.80
Purchase #3	$32.61	4.615%	$34.115	$34.12	$34.10	$34.10
Purchase #4	$54.99	7.433%	$59.0774	$59.08	$59.10	$59.10
Purchase #5	$103.95	6.650%	$110.8627	$110.86	$110.85	$110.90
Purchase #6	$71.29	9.472%	$78.0426	$78.04	$78.05	$78.00
Purchase #7	$172.66	4.122%	$179.777	$179.78	$179.80	$179.80
7 purchase totals =	$795.73		$844.6935	$844.70	$844.75	$844.70