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	$93.57	7.475%	$100.5644	$100.56	$100.55	$100.60
Purchase #2	$11.85	13.697%	$13.4731	$13.47	$13.45	$13.50
Purchase #3	$181.83	12.266%	$204.1333	$204.13	$204.15	$204.10
Purchase #4	$117.80	8.851%	$128.2265	$128.23	$128.25	$128.20
Purchase #5	$156.57	7.854%	$168.867	$168.87	$168.85	$168.90
Purchase #6	$107.38	7.172%	$115.0813	$115.08	$115.10	$115.10
Purchase #7	$131.59	8.142%	$142.3041	$142.30	$142.30	$142.30
7 purchase totals =	$800.59		$872.6497	$872.64	$872.65	$872.70