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	$213.76	9.649%	$234.3857	$234.39	$234.40	$234.40
Purchase #2	$105.90	3.104%	$109.1871	$109.19	$109.20	$109.20
Purchase #3	$225.92	13.681%	$256.8281	$256.83	$256.85	$256.80
Purchase #4	$72.53	8.184%	$78.4659	$78.47	$78.45	$78.50
Purchase #5	$106.37	9.594%	$116.5751	$116.58	$116.60	$116.60
Purchase #6	$194.83	11.323%	$216.8906	$216.89	$216.90	$216.90
Purchase #7	$102.96	13.777%	$117.1448	$117.14	$117.15	$117.10
7 purchase totals =	$1,022.27		$1,129.4773	$1,129.49	$1,129.55	$1,129.50