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	$244.44	8.758%	$265.8481	$265.85	$265.85	$265.80
Purchase #2	$197.45	12.665%	$222.457	$222.46	$222.45	$222.50
Purchase #3	$80.72	8.391%	$87.4932	$87.49	$87.50	$87.50
Purchase #4	$226.27	10.702%	$250.4854	$250.49	$250.50	$250.50
Purchase #5	$164.49	3.857%	$170.8344	$170.83	$170.85	$170.80
Purchase #6	$118.54	11.127%	$131.7299	$131.73	$131.75	$131.70
Purchase #7	$5.54	5.389%	$5.8386	$5.84	$5.85	$5.80
7 purchase totals =	$1,037.45		$1,134.6866	$1,134.69	$1,134.75	$1,134.60