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	$98.86	13.733%	$112.4364	$112.44	$112.45	$112.40
Purchase #2	$68.80	4.828%	$72.1217	$72.12	$72.10	$72.10
Purchase #3	$226.86	10.345%	$250.3287	$250.33	$250.35	$250.30
Purchase #4	$229.73	4.448%	$239.9484	$239.95	$239.95	$239.90
Purchase #5	$188.43	3.542%	$195.1042	$195.10	$195.10	$195.10
Purchase #6	$88.58	12.509%	$99.6605	$99.66	$99.65	$99.70
Purchase #7	$67.46	9.466%	$73.8458	$73.85	$73.85	$73.80
7 purchase totals =	$968.72		$1,043.4457	$1,043.45	$1,043.45	$1,043.30