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	$59.76	9.554%	$65.4695	$65.47	$65.45	$65.50
Purchase #2	$225.55	5.705%	$238.4176	$238.42	$238.40	$238.40
Purchase #3	$142.41	6.565%	$151.7592	$151.76	$151.75	$151.80
Purchase #4	$13.71	4.442%	$14.319	$14.32	$14.30	$14.30
Purchase #5	$146.43	13.206%	$165.7675	$165.77	$165.75	$165.80
Purchase #6	$87.47	8.398%	$94.8157	$94.82	$94.80	$94.80
Purchase #7	$29.74	6.366%	$31.6332	$31.63	$31.65	$31.60
7 purchase totals =	$705.07		$762.1817	$762.19	$762.10	$762.20