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	$103.83	13.529%	$117.8772	$117.88	$117.90	$117.90
Purchase #2	$96.72	4.390%	$100.966	$100.97	$100.95	$101.00
Purchase #3	$192.31	10.133%	$211.7968	$211.80	$211.80	$211.80
Purchase #4	$58.45	13.561%	$66.3764	$66.38	$66.40	$66.40
Purchase #5	$176.78	3.850%	$183.586	$183.59	$183.60	$183.60
Purchase #6	$69.33	6.159%	$73.6	$73.60	$73.60	$73.60
Purchase #7	$37.62	7.122%	$40.2993	$40.30	$40.30	$40.30
7 purchase totals =	$735.04		$794.5017	$794.52	$794.55	$794.60