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	$217.43	9.810%	$238.7599	$238.76	$238.75	$238.80
Purchase #2	$108.42	10.336%	$119.6263	$119.63	$119.65	$119.60
Purchase #3	$64.51	10.764%	$71.4539	$71.45	$71.45	$71.50
Purchase #4	$98.56	5.117%	$103.6033	$103.60	$103.60	$103.60
Purchase #5	$36.29	9.731%	$39.8214	$39.82	$39.80	$39.80
Purchase #6	$60.89	4.268%	$63.4888	$63.49	$63.50	$63.50
Purchase #7	$49.51	6.802%	$52.8777	$52.88	$52.90	$52.90
7 purchase totals =	$635.61		$689.6313	$689.63	$689.65	$689.70