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	$197.73	10.389%	$218.2722	$218.27	$218.25	$218.30
Purchase #2	$44.61	5.622%	$47.118	$47.12	$47.10	$47.10
Purchase #3	$85.41	13.460%	$96.9062	$96.91	$96.90	$96.90
Purchase #4	$30.59	12.555%	$34.4306	$34.43	$34.45	$34.40
Purchase #5	$145.72	5.453%	$153.6661	$153.67	$153.65	$153.70
Purchase #6	$126.82	3.471%	$131.2219	$131.22	$131.20	$131.20
Purchase #7	$87.93	12.625%	$99.0312	$99.03	$99.05	$99.00
7 purchase totals =	$718.81		$780.6462	$780.65	$780.60	$780.60