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	$112.77	4.223%	$117.5323	$117.53	$117.55	$117.50
Purchase #2	$145.46	12.329%	$163.3938	$163.39	$163.40	$163.40
Purchase #3	$116.88	13.428%	$132.5746	$132.57	$132.55	$132.60
Purchase #4	$140.56	11.110%	$156.1762	$156.18	$156.20	$156.20
Purchase #5	$235.68	6.462%	$250.9096	$250.91	$250.90	$250.90
Purchase #6	$215.65	4.119%	$224.5326	$224.53	$224.55	$224.50
Purchase #7	$74.64	10.321%	$82.3436	$82.34	$82.35	$82.30
7 purchase totals =	$1,041.64		$1,127.4627	$1,127.45	$1,127.50	$1,127.40