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	$208.93	6.529%	$222.571	$222.57	$222.55	$222.60
Purchase #2	$127.80	13.177%	$144.6402	$144.64	$144.65	$144.60
Purchase #3	$201.64	10.163%	$222.1327	$222.13	$222.15	$222.10
Purchase #4	$122.40	12.128%	$137.2447	$137.24	$137.25	$137.20
Purchase #5	$249.66	6.450%	$265.7631	$265.76	$265.75	$265.80
Purchase #6	$29.83	12.873%	$33.67	$33.67	$33.65	$33.70
Purchase #7	$59.90	5.415%	$63.1436	$63.14	$63.15	$63.10
7 purchase totals =	$1,000.16		$1,089.1653	$1,089.15	$1,089.15	$1,089.10