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	$223.63	3.370%	$231.1663	$231.17	$231.15	$231.20
Purchase #2	$187.45	3.252%	$193.5459	$193.55	$193.55	$193.50
Purchase #3	$49.82	10.584%	$55.0929	$55.09	$55.10	$55.10
Purchase #4	$241.69	6.114%	$256.4669	$256.47	$256.45	$256.50
Purchase #5	$249.60	10.382%	$275.5135	$275.51	$275.50	$275.50
Purchase #6	$101.69	9.868%	$111.7248	$111.72	$111.70	$111.70
Purchase #7	$139.45	7.718%	$150.2128	$150.21	$150.20	$150.20
7 purchase totals =	$1,193.33		$1,273.7231	$1,273.72	$1,273.65	$1,273.70