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	$234.51	10.351%	$258.7841	$258.78	$258.80	$258.80
Purchase #2	$209.55	4.541%	$219.0657	$219.07	$219.05	$219.10
Purchase #3	$54.65	12.369%	$61.4097	$61.41	$61.40	$61.40
Purchase #4	$165.98	6.228%	$176.3172	$176.32	$176.30	$176.30
Purchase #5	$9.36	7.757%	$10.0861	$10.09	$10.10	$10.10
Purchase #6	$159.46	4.385%	$166.4523	$166.45	$166.45	$166.50
Purchase #7	$111.76	4.277%	$116.54	$116.54	$116.55	$116.50
7 purchase totals =	$945.27		$1,008.6551	$1,008.66	$1,008.65	$1,008.70