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	$155.83	9.430%	$170.5248	$170.52	$170.50	$170.50
Purchase #2	$207.29	9.716%	$227.4303	$227.43	$227.45	$227.40
Purchase #3	$85.60	5.438%	$90.2549	$90.25	$90.25	$90.30
Purchase #4	$43.38	7.489%	$46.6287	$46.63	$46.65	$46.60
Purchase #5	$159.31	7.429%	$171.1451	$171.15	$171.15	$171.10
Purchase #6	$104.98	4.705%	$109.9193	$109.92	$109.90	$109.90
Purchase #7	$219.55	3.808%	$227.9105	$227.91	$227.90	$227.90
7 purchase totals =	$975.94		$1,043.8136	$1,043.81	$1,043.80	$1,043.70