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	$41.35	12.276%	$46.4261	$46.43	$46.45	$46.40
Purchase #2	$121.79	5.673%	$128.6991	$128.70	$128.70	$128.70
Purchase #3	$98.94	7.475%	$106.3358	$106.34	$106.35	$106.30
Purchase #4	$112.78	8.574%	$122.4498	$122.45	$122.45	$122.40
Purchase #5	$101.25	9.640%	$111.0105	$111.01	$111.00	$111.00
Purchase #6	$164.68	9.632%	$180.542	$180.54	$180.55	$180.50
Purchase #7	$41.44	3.403%	$42.8502	$42.85	$42.85	$42.90
7 purchase totals =	$682.23		$738.3135	$738.32	$738.35	$738.20