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	$213.30	11.255%	$237.3069	$237.31	$237.30	$237.30
Purchase #2	$83.97	12.630%	$94.5754	$94.58	$94.60	$94.60
Purchase #3	$179.48	3.713%	$186.1441	$186.14	$186.15	$186.10
Purchase #4	$167.65	4.154%	$174.6142	$174.61	$174.60	$174.60
Purchase #5	$221.98	7.649%	$238.9593	$238.96	$238.95	$239.00
Purchase #6	$48.37	5.300%	$50.9336	$50.93	$50.95	$50.90
Purchase #7	$57.52	3.210%	$59.3664	$59.37	$59.35	$59.40
7 purchase totals =	$972.27		$1,041.8999	$1,041.90	$1,041.90	$1,041.90