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	$144.88	5.558%	$152.9324	$152.93	$152.95	$152.90
Purchase #2	$112.73	4.315%	$117.5943	$117.59	$117.60	$117.60
Purchase #3	$130.85	4.446%	$136.6676	$136.67	$136.65	$136.70
Purchase #4	$108.88	7.125%	$116.6377	$116.64	$116.65	$116.60
Purchase #5	$54.78	9.419%	$59.9397	$59.94	$59.95	$59.90
Purchase #6	$179.86	3.360%	$185.9033	$185.90	$185.90	$185.90
Purchase #7	$25.42	11.513%	$28.3466	$28.35	$28.35	$28.30
7 purchase totals =	$757.40		$798.0216	$798.02	$798.05	$797.90