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	$206.47	11.141%	$229.4728	$229.47	$229.45	$229.50
Purchase #2	$184.66	6.571%	$196.794	$196.79	$196.80	$196.80
Purchase #3	$196.43	11.423%	$218.8682	$218.87	$218.85	$218.90
Purchase #4	$165.33	8.289%	$179.0342	$179.03	$179.05	$179.00
Purchase #5	$13.60	5.379%	$14.3315	$14.33	$14.35	$14.30
Purchase #6	$177.56	13.157%	$200.9216	$200.92	$200.90	$200.90
Purchase #7	$218.85	5.668%	$231.2544	$231.25	$231.25	$231.30
7 purchase totals =	$1,162.90		$1,270.6767	$1,270.66	$1,270.65	$1,270.70