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	$51.86	11.178%	$57.6569	$57.66	$57.65	$57.70
Purchase #2	$48.64	7.765%	$52.4169	$52.42	$52.40	$52.40
Purchase #3	$178.45	6.745%	$190.4865	$190.49	$190.50	$190.50
Purchase #4	$126.49	13.364%	$143.3941	$143.39	$143.40	$143.40
Purchase #5	$156.77	5.589%	$165.5319	$165.53	$165.55	$165.50
Purchase #6	$137.70	12.154%	$154.4361	$154.44	$154.45	$154.40
Purchase #7	$161.48	12.568%	$181.7748	$181.77	$181.75	$181.80
7 purchase totals =	$861.39		$945.6972	$945.70	$945.70	$945.70