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	$237.44	4.660%	$248.5047	$248.50	$248.50	$248.50
Purchase #2	$72.37	11.821%	$80.9249	$80.92	$80.90	$80.90
Purchase #3	$198.39	8.586%	$215.4238	$215.42	$215.40	$215.40
Purchase #4	$99.59	11.584%	$111.1265	$111.13	$111.15	$111.10
Purchase #5	$208.35	12.309%	$233.9958	$234.00	$234.00	$234.00
Purchase #6	$204.96	7.297%	$219.9159	$219.92	$219.90	$219.90
Purchase #7	$74.65	5.342%	$78.6378	$78.64	$78.65	$78.60
7 purchase totals =	$1,095.75		$1,188.5294	$1,188.53	$1,188.50	$1,188.40