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	$161.41	7.598%	$173.6739	$173.67	$173.65	$173.70
Purchase #2	$219.40	12.839%	$247.5688	$247.57	$247.55	$247.60
Purchase #3	$216.60	7.703%	$233.2847	$233.28	$233.30	$233.30
Purchase #4	$174.98	12.304%	$196.5095	$196.51	$196.50	$196.50
Purchase #5	$19.83	10.667%	$21.9453	$21.95	$21.95	$21.90
Purchase #6	$169.60	7.250%	$181.896	$181.90	$181.90	$181.90
Purchase #7	$40.58	11.837%	$45.3835	$45.38	$45.40	$45.40
7 purchase totals =	$1,002.40		$1,100.2617	$1,100.26	$1,100.25	$1,100.30