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	$11.83	10.359%	$13.0555	$13.06	$13.05	$13.10
Purchase #2	$205.58	8.194%	$222.4252	$222.43	$222.45	$222.40
Purchase #3	$179.76	11.723%	$200.8333	$200.83	$200.85	$200.80
Purchase #4	$94.87	3.459%	$98.1516	$98.15	$98.15	$98.20
Purchase #5	$250.48	4.648%	$262.1223	$262.12	$262.10	$262.10
Purchase #6	$41.99	6.748%	$44.8235	$44.82	$44.80	$44.80
Purchase #7	$178.52	12.579%	$200.976	$200.98	$201.00	$201.00
7 purchase totals =	$963.03		$1,042.3874	$1,042.39	$1,042.40	$1,042.40