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	$119.90	11.134%	$133.2497	$133.25	$133.25	$133.20
Purchase #2	$241.46	11.629%	$269.5394	$269.54	$269.55	$269.50
Purchase #3	$196.80	9.460%	$215.4173	$215.42	$215.40	$215.40
Purchase #4	$119.25	13.117%	$134.892	$134.89	$134.90	$134.90
Purchase #5	$57.37	4.440%	$59.9172	$59.92	$59.90	$59.90
Purchase #6	$141.60	4.296%	$147.6831	$147.68	$147.70	$147.70
Purchase #7	$106.83	8.641%	$116.0612	$116.06	$116.05	$116.10
7 purchase totals =	$983.21		$1,076.7599	$1,076.76	$1,076.75	$1,076.70