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	$152.35	10.695%	$168.6438	$168.64	$168.65	$168.60
Purchase #2	$214.72	13.585%	$243.8897	$243.89	$243.90	$243.90
Purchase #3	$18.58	9.729%	$20.3876	$20.39	$20.40	$20.40
Purchase #4	$19.51	7.254%	$20.9253	$20.93	$20.95	$20.90
Purchase #5	$108.97	5.414%	$114.8696	$114.87	$114.85	$114.90
Purchase #6	$214.84	9.800%	$235.8943	$235.89	$235.90	$235.90
Purchase #7	$134.41	11.659%	$150.0809	$150.08	$150.10	$150.10
7 purchase totals =	$863.38		$954.6912	$954.69	$954.75	$954.70