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	$63.60	4.206%	$66.275	$66.28	$66.30	$66.30
Purchase #2	$19.33	11.222%	$21.4992	$21.50	$21.50	$21.50
Purchase #3	$86.29	8.150%	$93.3226	$93.32	$93.30	$93.30
Purchase #4	$87.77	12.780%	$98.987	$98.99	$99.00	$99.00
Purchase #5	$46.64	3.460%	$48.2537	$48.25	$48.25	$48.30
Purchase #6	$38.41	12.832%	$43.3388	$43.34	$43.35	$43.30
Purchase #7	$159.32	5.720%	$168.4331	$168.43	$168.45	$168.40
7 purchase totals =	$501.36		$540.1094	$540.11	$540.15	$540.10