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	$32.97	7.336%	$35.3887	$35.39	$35.40	$35.40
Purchase #2	$245.46	10.529%	$271.3045	$271.30	$271.30	$271.30
Purchase #3	$109.89	7.421%	$118.0449	$118.04	$118.05	$118.00
Purchase #4	$107.25	4.116%	$111.6644	$111.66	$111.65	$111.70
Purchase #5	$210.80	5.632%	$222.6723	$222.67	$222.65	$222.70
Purchase #6	$132.81	7.105%	$142.2462	$142.25	$142.25	$142.20
Purchase #7	$18.67	12.603%	$21.023	$21.02	$21.00	$21.00
7 purchase totals =	$857.85		$922.3440	$922.33	$922.30	$922.30