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	$97.76	13.817%	$111.2675	$111.27	$111.25	$111.30
Purchase #2	$176.33	10.691%	$195.1814	$195.18	$195.20	$195.20
Purchase #3	$241.28	3.565%	$249.8816	$249.88	$249.90	$249.90
Purchase #4	$46.43	10.748%	$51.4203	$51.42	$51.40	$51.40
Purchase #5	$70.38	3.577%	$72.8975	$72.90	$72.90	$72.90
Purchase #6	$204.89	3.676%	$212.4218	$212.42	$212.40	$212.40
Purchase #7	$66.29	7.601%	$71.3287	$71.33	$71.35	$71.30
7 purchase totals =	$903.36		$964.3988	$964.40	$964.40	$964.40