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	$239.96	3.115%	$247.4348	$247.43	$247.45	$247.40
Purchase #2	$78.39	8.563%	$85.1025	$85.10	$85.10	$85.10
Purchase #3	$47.49	5.419%	$50.0635	$50.06	$50.05	$50.10
Purchase #4	$128.92	8.139%	$139.4128	$139.41	$139.40	$139.40
Purchase #5	$148.70	5.275%	$156.5439	$156.54	$156.55	$156.50
Purchase #6	$156.72	10.457%	$173.1082	$173.11	$173.10	$173.10
Purchase #7	$182.89	8.473%	$198.3863	$198.39	$198.40	$198.40
7 purchase totals =	$983.07		$1,050.0520	$1,050.04	$1,050.05	$1,050.00