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	$186.99	5.276%	$196.8556	$196.86	$196.85	$196.90
Purchase #2	$72.32	8.281%	$78.3088	$78.31	$78.30	$78.30
Purchase #3	$107.45	12.748%	$121.1477	$121.15	$121.15	$121.10
Purchase #4	$54.55	9.592%	$59.7824	$59.78	$59.80	$59.80
Purchase #5	$58.69	12.778%	$66.1894	$66.19	$66.20	$66.20
Purchase #6	$200.41	7.826%	$216.0941	$216.09	$216.10	$216.10
Purchase #7	$237.72	10.191%	$261.946	$261.95	$261.95	$261.90
7 purchase totals =	$918.13		$1,000.3240	$1,000.33	$1,000.35	$1,000.30