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	$42.64	10.317%	$47.0392	$47.04	$47.05	$47.00
Purchase #2	$121.80	4.822%	$127.6732	$127.67	$127.65	$127.70
Purchase #3	$137.44	3.615%	$142.4085	$142.41	$142.40	$142.40
Purchase #4	$217.88	10.549%	$240.8642	$240.86	$240.85	$240.90
Purchase #5	$250.45	4.151%	$260.8462	$260.85	$260.85	$260.80
Purchase #6	$140.65	8.225%	$152.2185	$152.22	$152.20	$152.20
Purchase #7	$107.83	5.614%	$113.8836	$113.88	$113.90	$113.90
7 purchase totals =	$1,018.69		$1,084.9334	$1,084.93	$1,084.90	$1,084.90