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	$211.70	9.823%	$232.4953	$232.50	$232.50	$232.50
Purchase #2	$238.31	12.750%	$268.6945	$268.69	$268.70	$268.70
Purchase #3	$29.51	11.246%	$32.8287	$32.83	$32.85	$32.80
Purchase #4	$68.42	6.238%	$72.688	$72.69	$72.70	$72.70
Purchase #5	$179.63	6.667%	$191.6059	$191.61	$191.60	$191.60
Purchase #6	$191.41	13.511%	$217.2714	$217.27	$217.25	$217.30
Purchase #7	$201.33	8.241%	$217.9216	$217.92	$217.90	$217.90
7 purchase totals =	$1,120.31		$1,233.5054	$1,233.51	$1,233.50	$1,233.50