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	$179.78	6.150%	$190.8365	$190.84	$190.85	$190.80
Purchase #2	$241.76	13.703%	$274.8884	$274.89	$274.90	$274.90
Purchase #3	$162.53	7.642%	$174.9505	$174.95	$174.95	$175.00
Purchase #4	$30.44	13.856%	$34.6578	$34.66	$34.65	$34.70
Purchase #5	$128.37	3.559%	$132.9387	$132.94	$132.95	$132.90
Purchase #6	$91.59	11.872%	$102.4636	$102.46	$102.45	$102.50
Purchase #7	$160.88	12.562%	$181.0897	$181.09	$181.10	$181.10
7 purchase totals =	$995.35		$1,091.8252	$1,091.83	$1,091.85	$1,091.90