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	$112.56	13.657%	$127.9323	$127.93	$127.95	$127.90
Purchase #2	$39.32	10.579%	$43.4797	$43.48	$43.50	$43.50
Purchase #3	$121.61	9.321%	$132.9453	$132.95	$132.95	$132.90
Purchase #4	$154.61	9.145%	$168.7491	$168.75	$168.75	$168.70
Purchase #5	$64.61	7.376%	$69.3756	$69.38	$69.40	$69.40
Purchase #6	$169.92	5.750%	$179.6904	$179.69	$179.70	$179.70
Purchase #7	$105.96	4.793%	$111.0387	$111.04	$111.05	$111.00
7 purchase totals =	$768.59		$833.2111	$833.22	$833.30	$833.10