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	$173.83	10.243%	$191.6354	$191.64	$191.65	$191.60
Purchase #2	$113.73	8.232%	$123.0923	$123.09	$123.10	$123.10
Purchase #3	$60.98	3.183%	$62.921	$62.92	$62.90	$62.90
Purchase #4	$225.92	11.271%	$251.3834	$251.38	$251.40	$251.40
Purchase #5	$38.63	6.439%	$41.1174	$41.12	$41.10	$41.10
Purchase #6	$6.51	9.651%	$7.1383	$7.14	$7.15	$7.10
Purchase #7	$225.90	13.477%	$256.3445	$256.34	$256.35	$256.30
7 purchase totals =	$845.50		$933.6323	$933.63	$933.65	$933.50