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	$9.92	3.336%	$10.2509	$10.25	$10.25	$10.30
Purchase #2	$153.80	9.409%	$168.271	$168.27	$168.25	$168.30
Purchase #3	$186.81	12.151%	$209.5093	$209.51	$209.50	$209.50
Purchase #4	$118.70	13.150%	$134.3091	$134.31	$134.30	$134.30
Purchase #5	$226.88	8.444%	$246.0377	$246.04	$246.05	$246.00
Purchase #6	$75.92	5.833%	$80.3484	$80.35	$80.35	$80.30
Purchase #7	$206.86	5.116%	$217.443	$217.44	$217.45	$217.40
7 purchase totals =	$978.89		$1,066.1694	$1,066.17	$1,066.15	$1,066.10