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	$199.60	7.248%	$214.067	$214.07	$214.05	$214.10
Purchase #2	$140.31	7.615%	$150.9946	$150.99	$151.00	$151.00
Purchase #3	$190.32	4.826%	$199.5048	$199.50	$199.50	$199.50
Purchase #4	$54.51	6.190%	$57.8842	$57.88	$57.90	$57.90
Purchase #5	$110.25	6.111%	$116.9874	$116.99	$117.00	$117.00
Purchase #6	$82.75	8.705%	$89.9534	$89.95	$89.95	$90.00
Purchase #7	$112.57	13.125%	$127.3448	$127.34	$127.35	$127.30
7 purchase totals =	$890.31		$956.7362	$956.72	$956.75	$956.80