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	$40.32	8.356%	$43.6891	$43.69	$43.70	$43.70
Purchase #2	$53.75	5.858%	$56.8987	$56.90	$56.90	$56.90
Purchase #3	$100.66	13.706%	$114.4565	$114.46	$114.45	$114.50
Purchase #4	$34.81	7.530%	$37.4312	$37.43	$37.45	$37.40
Purchase #5	$248.49	3.372%	$256.8691	$256.87	$256.85	$256.90
Purchase #6	$182.90	12.704%	$206.1356	$206.14	$206.15	$206.10
Purchase #7	$150.80	11.767%	$168.5446	$168.54	$168.55	$168.50
7 purchase totals =	$811.73		$884.0248	$884.03	$884.05	$884.00