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	$231.69	9.828%	$254.4605	$254.46	$254.45	$254.50
Purchase #2	$151.51	11.446%	$168.8518	$168.85	$168.85	$168.90
Purchase #3	$46.42	4.458%	$48.4894	$48.49	$48.50	$48.50
Purchase #4	$32.83	4.181%	$34.2026	$34.20	$34.20	$34.20
Purchase #5	$28.46	10.857%	$31.5499	$31.55	$31.55	$31.50
Purchase #6	$166.35	7.732%	$179.2122	$179.21	$179.20	$179.20
Purchase #7	$143.98	11.354%	$160.3275	$160.33	$160.35	$160.30
7 purchase totals =	$801.24		$877.0939	$877.09	$877.10	$877.10