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	$83.60	8.408%	$90.6291	$90.63	$90.65	$90.60
Purchase #2	$167.27	11.812%	$187.0279	$187.03	$187.05	$187.00
Purchase #3	$227.76	9.859%	$250.2149	$250.21	$250.20	$250.20
Purchase #4	$58.64	12.769%	$66.1277	$66.13	$66.15	$66.10
Purchase #5	$246.55	6.623%	$262.879	$262.88	$262.90	$262.90
Purchase #6	$79.84	3.385%	$82.5426	$82.54	$82.55	$82.50
Purchase #7	$128.65	4.367%	$134.2681	$134.27	$134.25	$134.30
7 purchase totals =	$992.31		$1,073.6893	$1,073.69	$1,073.75	$1,073.60