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	$201.98	13.632%	$229.5139	$229.51	$229.50	$229.50
Purchase #2	$42.95	10.781%	$47.5804	$47.58	$47.60	$47.60
Purchase #3	$144.96	3.857%	$150.5511	$150.55	$150.55	$150.60
Purchase #4	$151.72	9.599%	$166.2836	$166.28	$166.30	$166.30
Purchase #5	$178.83	9.834%	$196.4161	$196.42	$196.40	$196.40
Purchase #6	$5.82	13.165%	$6.5862	$6.59	$6.60	$6.60
Purchase #7	$67.97	12.343%	$76.3595	$76.36	$76.35	$76.40
7 purchase totals =	$794.23		$873.2908	$873.29	$873.30	$873.40