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	$192.38	9.296%	$210.2636	$210.26	$210.25	$210.30
Purchase #2	$119.37	6.455%	$127.0753	$127.08	$127.10	$127.10
Purchase #3	$84.93	5.141%	$89.2963	$89.30	$89.30	$89.30
Purchase #4	$98.57	7.462%	$105.9253	$105.93	$105.95	$105.90
Purchase #5	$91.61	12.638%	$103.1877	$103.19	$103.20	$103.20
Purchase #6	$62.25	4.641%	$65.139	$65.14	$65.15	$65.10
Purchase #7	$86.76	8.846%	$94.4348	$94.43	$94.45	$94.40
7 purchase totals =	$735.87		$795.3220	$795.33	$795.40	$795.30