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	$84.51	3.655%	$87.5988	$87.60	$87.60	$87.60
Purchase #2	$128.54	10.776%	$142.3915	$142.39	$142.40	$142.40
Purchase #3	$123.80	10.811%	$137.184	$137.18	$137.20	$137.20
Purchase #4	$246.81	11.784%	$275.8941	$275.89	$275.90	$275.90
Purchase #5	$5.95	5.791%	$6.2946	$6.29	$6.30	$6.30
Purchase #6	$108.39	4.212%	$112.9554	$112.96	$112.95	$113.00
Purchase #7	$127.47	3.742%	$132.2399	$132.24	$132.25	$132.20
7 purchase totals =	$825.47		$894.5583	$894.55	$894.60	$894.60