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	$93.61	12.598%	$105.403	$105.40	$105.40	$105.40
Purchase #2	$160.98	8.460%	$174.5989	$174.60	$174.60	$174.60
Purchase #3	$140.70	11.291%	$156.5864	$156.59	$156.60	$156.60
Purchase #4	$89.34	8.510%	$96.9428	$96.94	$96.95	$96.90
Purchase #5	$225.51	8.204%	$244.0108	$244.01	$244.00	$244.00
Purchase #6	$136.27	10.551%	$150.6478	$150.65	$150.65	$150.60
Purchase #7	$198.45	6.625%	$211.5973	$211.60	$211.60	$211.60
7 purchase totals =	$1,044.86		$1,139.7870	$1,139.79	$1,139.80	$1,139.70