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	$119.65	7.212%	$128.2792	$128.28	$128.30	$128.30
Purchase #2	$59.90	3.471%	$61.9791	$61.98	$62.00	$62.00
Purchase #3	$115.98	13.476%	$131.6095	$131.61	$131.60	$131.60
Purchase #4	$56.66	8.363%	$61.3985	$61.40	$61.40	$61.40
Purchase #5	$139.69	9.855%	$153.4564	$153.46	$153.45	$153.50
Purchase #6	$181.77	6.590%	$193.7486	$193.75	$193.75	$193.70
Purchase #7	$52.90	3.372%	$54.6838	$54.68	$54.70	$54.70
7 purchase totals =	$726.55		$785.1551	$785.16	$785.20	$785.20