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	$5.43	4.815%	$5.6915	$5.69	$5.70	$5.70
Purchase #2	$242.93	13.403%	$275.4899	$275.49	$275.50	$275.50
Purchase #3	$47.25	5.371%	$49.7878	$49.79	$49.80	$49.80
Purchase #4	$213.27	4.796%	$223.4984	$223.50	$223.50	$223.50
Purchase #5	$186.34	7.296%	$199.9354	$199.94	$199.95	$199.90
Purchase #6	$29.31	10.255%	$32.3157	$32.32	$32.30	$32.30
Purchase #7	$196.30	11.296%	$218.474	$218.47	$218.45	$218.50
7 purchase totals =	$920.83		$1,005.1927	$1,005.20	$1,005.20	$1,005.20