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	$126.51	11.328%	$140.8411	$140.84	$140.85	$140.80
Purchase #2	$215.30	3.294%	$222.392	$222.39	$222.40	$222.40
Purchase #3	$197.61	3.691%	$204.9038	$204.90	$204.90	$204.90
Purchase #4	$34.91	10.323%	$38.5138	$38.51	$38.50	$38.50
Purchase #5	$193.71	9.408%	$211.9342	$211.93	$211.95	$211.90
Purchase #6	$41.41	12.844%	$46.7287	$46.73	$46.75	$46.70
Purchase #7	$208.93	12.336%	$234.7036	$234.70	$234.70	$234.70
7 purchase totals =	$1,018.38		$1,100.0172	$1,100.00	$1,100.05	$1,099.90