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	$234.78	13.491%	$266.4542	$266.45	$266.45	$266.50
Purchase #2	$178.82	11.178%	$198.8085	$198.81	$198.80	$198.80
Purchase #3	$86.70	13.530%	$98.4305	$98.43	$98.45	$98.40
Purchase #4	$151.69	8.183%	$164.1028	$164.10	$164.10	$164.10
Purchase #5	$37.66	9.459%	$41.2223	$41.22	$41.20	$41.20
Purchase #6	$30.72	5.438%	$32.3906	$32.39	$32.40	$32.40
Purchase #7	$123.94	10.399%	$136.8285	$136.83	$136.85	$136.80
7 purchase totals =	$844.31		$938.2374	$938.23	$938.25	$938.20