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	$203.73	10.481%	$225.0829	$225.08	$225.10	$225.10
Purchase #2	$170.57	10.575%	$188.6078	$188.61	$188.60	$188.60
Purchase #3	$39.90	8.421%	$43.26	$43.26	$43.25	$43.30
Purchase #4	$50.91	6.114%	$54.0226	$54.02	$54.00	$54.00
Purchase #5	$237.58	6.691%	$253.4765	$253.48	$253.50	$253.50
Purchase #6	$62.58	6.209%	$66.4656	$66.47	$66.45	$66.50
Purchase #7	$66.57	9.493%	$72.8895	$72.89	$72.90	$72.90
7 purchase totals =	$831.84		$903.8049	$903.81	$903.80	$903.90