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	$156.45	8.104%	$169.1287	$169.13	$169.15	$169.10
Purchase #2	$187.87	13.275%	$212.8097	$212.81	$212.80	$212.80
Purchase #3	$91.64	12.617%	$103.2022	$103.20	$103.20	$103.20
Purchase #4	$172.36	13.820%	$196.1802	$196.18	$196.20	$196.20
Purchase #5	$189.39	10.278%	$208.8555	$208.86	$208.85	$208.90
Purchase #6	$150.51	6.761%	$160.686	$160.69	$160.70	$160.70
Purchase #7	$215.45	4.422%	$224.9772	$224.98	$225.00	$225.00
7 purchase totals =	$1,163.67		$1,275.8395	$1,275.85	$1,275.90	$1,275.90