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	$238.52	11.246%	$265.344	$265.34	$265.35	$265.30
Purchase #2	$43.38	11.629%	$48.4247	$48.42	$48.40	$48.40
Purchase #3	$74.42	10.698%	$82.3815	$82.38	$82.40	$82.40
Purchase #4	$130.58	8.762%	$142.0214	$142.02	$142.00	$142.00
Purchase #5	$234.66	12.862%	$264.842	$264.84	$264.85	$264.80
Purchase #6	$246.94	11.113%	$274.3824	$274.38	$274.40	$274.40
Purchase #7	$69.90	10.724%	$77.3961	$77.40	$77.40	$77.40
7 purchase totals =	$1,038.40		$1,154.7921	$1,154.78	$1,154.80	$1,154.70