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	$117.29	13.165%	$132.7312	$132.73	$132.75	$132.70
Purchase #2	$65.72	10.801%	$72.8184	$72.82	$72.80	$72.80
Purchase #3	$164.49	6.191%	$174.6736	$174.67	$174.65	$174.70
Purchase #4	$141.40	9.784%	$155.2346	$155.23	$155.25	$155.20
Purchase #5	$99.44	11.813%	$111.1868	$111.19	$111.20	$111.20
Purchase #6	$150.46	5.171%	$158.2403	$158.24	$158.25	$158.20
Purchase #7	$104.75	8.670%	$113.8318	$113.83	$113.85	$113.80
7 purchase totals =	$843.55		$918.7167	$918.71	$918.75	$918.60