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	$192.40	13.746%	$218.8473	$218.85	$218.85	$218.80
Purchase #2	$44.56	8.800%	$48.4813	$48.48	$48.50	$48.50
Purchase #3	$131.94	9.532%	$144.5165	$144.52	$144.50	$144.50
Purchase #4	$192.89	6.173%	$204.7971	$204.80	$204.80	$204.80
Purchase #5	$48.98	10.460%	$54.1033	$54.10	$54.10	$54.10
Purchase #6	$209.49	7.685%	$225.5893	$225.59	$225.60	$225.60
Purchase #7	$213.74	9.444%	$233.9256	$233.93	$233.95	$233.90
7 purchase totals =	$1,034.00		$1,130.2604	$1,130.27	$1,130.30	$1,130.20