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	$198.83	4.593%	$207.9623	$207.96	$207.95	$208.00
Purchase #2	$38.82	10.784%	$43.0063	$43.01	$43.00	$43.00
Purchase #3	$18.64	9.566%	$20.4231	$20.42	$20.40	$20.40
Purchase #4	$155.73	9.565%	$170.6256	$170.63	$170.65	$170.60
Purchase #5	$94.57	7.753%	$101.902	$101.90	$101.90	$101.90
Purchase #6	$53.70	7.775%	$57.8752	$57.88	$57.90	$57.90
Purchase #7	$85.78	5.598%	$90.582	$90.58	$90.60	$90.60
7 purchase totals =	$646.07		$692.3765	$692.38	$692.40	$692.40