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	$198.87	4.811%	$208.4376	$208.44	$208.45	$208.40
Purchase #2	$146.44	12.639%	$164.9486	$164.95	$164.95	$164.90
Purchase #3	$121.88	8.712%	$132.4982	$132.50	$132.50	$132.50
Purchase #4	$35.95	5.156%	$37.8036	$37.80	$37.80	$37.80
Purchase #5	$17.29	5.679%	$18.2719	$18.27	$18.25	$18.30
Purchase #6	$37.63	5.340%	$39.6394	$39.64	$39.65	$39.60
Purchase #7	$187.90	6.686%	$200.463	$200.46	$200.45	$200.50
7 purchase totals =	$745.96		$802.0623	$802.06	$802.05	$802.00