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	$235.66	10.169%	$259.6243	$259.62	$259.60	$259.60
Purchase #2	$241.38	8.505%	$261.9094	$261.91	$261.90	$261.90
Purchase #3	$190.63	9.434%	$208.614	$208.61	$208.60	$208.60
Purchase #4	$33.66	3.641%	$34.8856	$34.89	$34.90	$34.90
Purchase #5	$39.54	4.851%	$41.4581	$41.46	$41.45	$41.50
Purchase #6	$207.38	7.673%	$223.2923	$223.29	$223.30	$223.30
Purchase #7	$223.36	8.306%	$241.9123	$241.91	$241.90	$241.90
7 purchase totals =	$1,171.61		$1,271.6960	$1,271.69	$1,271.65	$1,271.70