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	$180.92	10.565%	$200.0342	$200.03	$200.05	$200.00
Purchase #2	$71.48	10.363%	$78.8875	$78.89	$78.90	$78.90
Purchase #3	$37.61	13.770%	$42.7889	$42.79	$42.80	$42.80
Purchase #4	$54.32	8.348%	$58.8546	$58.85	$58.85	$58.90
Purchase #5	$169.65	3.119%	$174.9414	$174.94	$174.95	$174.90
Purchase #6	$179.81	11.460%	$200.4162	$200.42	$200.40	$200.40
Purchase #7	$93.38	4.283%	$97.3795	$97.38	$97.40	$97.40
7 purchase totals =	$787.17		$853.3023	$853.30	$853.35	$853.30