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	$91.29	4.496%	$95.3944	$95.39	$95.40	$95.40
Purchase #2	$36.64	9.443%	$40.0999	$40.10	$40.10	$40.10
Purchase #3	$217.25	10.495%	$240.0504	$240.05	$240.05	$240.10
Purchase #4	$87.48	7.340%	$93.901	$93.90	$93.90	$93.90
Purchase #5	$173.88	6.589%	$185.337	$185.34	$185.35	$185.30
Purchase #6	$63.37	5.147%	$66.6317	$66.63	$66.65	$66.60
Purchase #7	$159.97	5.467%	$168.7156	$168.72	$168.70	$168.70
7 purchase totals =	$829.88		$890.1300	$890.13	$890.15	$890.10