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	$75.72	8.296%	$82.0017	$82.00	$82.00	$82.00
Purchase #2	$178.39	6.481%	$189.9515	$189.95	$189.95	$190.00
Purchase #3	$249.88	5.220%	$262.9237	$262.92	$262.90	$262.90
Purchase #4	$143.92	4.552%	$150.4712	$150.47	$150.45	$150.50
Purchase #5	$50.43	9.173%	$55.0559	$55.06	$55.05	$55.10
Purchase #6	$100.27	3.571%	$103.8506	$103.85	$103.85	$103.90
Purchase #7	$160.71	13.648%	$182.6437	$182.64	$182.65	$182.60
7 purchase totals =	$959.32		$1,026.8983	$1,026.89	$1,026.85	$1,027.00