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	$40.77	7.112%	$43.6696	$43.67	$43.65	$43.70
Purchase #2	$60.75	11.149%	$67.523	$67.52	$67.50	$67.50
Purchase #3	$65.45	7.781%	$70.5427	$70.54	$70.55	$70.50
Purchase #4	$165.72	8.809%	$180.3183	$180.32	$180.30	$180.30
Purchase #5	$186.83	7.660%	$201.1412	$201.14	$201.15	$201.10
Purchase #6	$195.91	4.678%	$205.0747	$205.07	$205.05	$205.10
Purchase #7	$238.82	4.600%	$249.8057	$249.81	$249.80	$249.80
7 purchase totals =	$954.25		$1,018.0752	$1,018.07	$1,018.00	$1,018.00