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	$137.78	10.817%	$152.6837	$152.68	$152.70	$152.70
Purchase #2	$63.81	12.388%	$71.7148	$71.71	$71.70	$71.70
Purchase #3	$203.79	5.782%	$215.5731	$215.57	$215.55	$215.60
Purchase #4	$240.56	8.275%	$260.4663	$260.47	$260.45	$260.50
Purchase #5	$60.81	9.250%	$66.4349	$66.43	$66.45	$66.40
Purchase #6	$64.29	11.820%	$71.8891	$71.89	$71.90	$71.90
Purchase #7	$198.84	3.642%	$206.0818	$206.08	$206.10	$206.10
7 purchase totals =	$969.88		$1,044.8437	$1,044.83	$1,044.85	$1,044.90