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	$105.34	8.108%	$113.881	$113.88	$113.90	$113.90
Purchase #2	$244.55	8.528%	$265.4052	$265.41	$265.40	$265.40
Purchase #3	$62.66	12.526%	$70.5088	$70.51	$70.50	$70.50
Purchase #4	$197.50	13.444%	$224.0519	$224.05	$224.05	$224.10
Purchase #5	$129.59	11.775%	$144.8492	$144.85	$144.85	$144.80
Purchase #6	$51.27	8.850%	$55.8074	$55.81	$55.80	$55.80
Purchase #7	$99.38	12.249%	$111.5531	$111.55	$111.55	$111.60
7 purchase totals =	$890.29		$986.0566	$986.06	$986.05	$986.10