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	$229.70	13.852%	$261.518	$261.52	$261.50	$261.50
Purchase #2	$136.93	5.720%	$144.7624	$144.76	$144.75	$144.80
Purchase #3	$105.50	3.632%	$109.3318	$109.33	$109.35	$109.30
Purchase #4	$233.45	6.192%	$247.9052	$247.91	$247.90	$247.90
Purchase #5	$38.54	8.351%	$41.7585	$41.76	$41.75	$41.80
Purchase #6	$161.31	11.397%	$179.6945	$179.69	$179.70	$179.70
Purchase #7	$22.66	12.380%	$25.4653	$25.47	$25.45	$25.50
7 purchase totals =	$928.09		$1,010.4357	$1,010.44	$1,010.40	$1,010.50