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	$205.29	8.648%	$223.0435	$223.04	$223.05	$223.00
Purchase #2	$41.31	9.329%	$45.1638	$45.16	$45.15	$45.20
Purchase #3	$234.29	6.637%	$249.8398	$249.84	$249.85	$249.80
Purchase #4	$97.63	11.785%	$109.1357	$109.14	$109.15	$109.10
Purchase #5	$43.87	5.598%	$46.3258	$46.33	$46.35	$46.30
Purchase #6	$158.33	8.528%	$171.8324	$171.83	$171.85	$171.80
Purchase #7	$147.68	10.773%	$163.5896	$163.59	$163.60	$163.60
7 purchase totals =	$928.40		$1,008.9306	$1,008.93	$1,009.00	$1,008.80