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	$76.83	13.298%	$87.0469	$87.05	$87.05	$87.00
Purchase #2	$221.65	9.356%	$242.3876	$242.39	$242.40	$242.40
Purchase #3	$27.96	5.259%	$29.4304	$29.43	$29.45	$29.40
Purchase #4	$84.40	13.197%	$95.5383	$95.54	$95.55	$95.50
Purchase #5	$83.93	7.606%	$90.3137	$90.31	$90.30	$90.30
Purchase #6	$138.63	13.842%	$157.8192	$157.82	$157.80	$157.80
Purchase #7	$120.77	5.410%	$127.3037	$127.30	$127.30	$127.30
7 purchase totals =	$754.17		$829.8398	$829.84	$829.85	$829.70