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	$136.53	7.584%	$146.8844	$146.88	$146.90	$146.90
Purchase #2	$215.38	9.513%	$235.8691	$235.87	$235.85	$235.90
Purchase #3	$179.53	7.468%	$192.9373	$192.94	$192.95	$192.90
Purchase #4	$38.71	13.189%	$43.8155	$43.82	$43.80	$43.80
Purchase #5	$52.62	4.162%	$54.81	$54.81	$54.80	$54.80
Purchase #6	$126.43	10.174%	$139.293	$139.29	$139.30	$139.30
Purchase #7	$191.37	9.471%	$209.4947	$209.49	$209.50	$209.50
7 purchase totals =	$940.57		$1,023.1040	$1,023.10	$1,023.10	$1,023.10