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	$34.75	3.229%	$35.8721	$35.87	$35.85	$35.90
Purchase #2	$25.35	12.212%	$28.4457	$28.45	$28.45	$28.40
Purchase #3	$152.39	9.825%	$167.3623	$167.36	$167.35	$167.40
Purchase #4	$90.50	11.847%	$101.2215	$101.22	$101.20	$101.20
Purchase #5	$86.93	3.639%	$90.0934	$90.09	$90.10	$90.10
Purchase #6	$163.52	9.755%	$179.4714	$179.47	$179.45	$179.50
Purchase #7	$240.94	13.554%	$273.597	$273.60	$273.60	$273.60
7 purchase totals =	$794.38		$876.0634	$876.06	$876.00	$876.10