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	$229.69	8.772%	$249.8384	$249.84	$249.85	$249.80
Purchase #2	$108.49	3.135%	$111.8912	$111.89	$111.90	$111.90
Purchase #3	$109.83	12.140%	$123.1634	$123.16	$123.15	$123.20
Purchase #4	$12.81	9.340%	$14.0065	$14.01	$14.00	$14.00
Purchase #5	$132.34	12.697%	$149.1432	$149.14	$149.15	$149.10
Purchase #6	$204.56	10.466%	$225.9692	$225.97	$225.95	$226.00
Purchase #7	$186.59	6.311%	$198.3657	$198.37	$198.35	$198.40
7 purchase totals =	$984.31		$1,072.3776	$1,072.38	$1,072.35	$1,072.40