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	$244.35	13.723%	$277.8822	$277.88	$277.90	$277.90
Purchase #2	$160.98	12.137%	$180.5181	$180.52	$180.50	$180.50
Purchase #3	$81.96	12.275%	$92.0206	$92.02	$92.00	$92.00
Purchase #4	$74.70	5.422%	$78.7502	$78.75	$78.75	$78.80
Purchase #5	$215.37	5.809%	$227.8808	$227.88	$227.90	$227.90
Purchase #6	$244.95	4.614%	$256.252	$256.25	$256.25	$256.30
Purchase #7	$38.98	5.751%	$41.2217	$41.22	$41.20	$41.20
7 purchase totals =	$1,061.29		$1,154.5256	$1,154.52	$1,154.50	$1,154.60