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	$143.29	6.141%	$152.0894	$152.09	$152.10	$152.10
Purchase #2	$156.91	9.624%	$172.011	$172.01	$172.00	$172.00
Purchase #3	$18.31	12.654%	$20.6269	$20.63	$20.65	$20.60
Purchase #4	$228.36	12.789%	$257.565	$257.57	$257.55	$257.60
Purchase #5	$10.89	12.597%	$12.2618	$12.26	$12.25	$12.30
Purchase #6	$198.43	10.123%	$218.5171	$218.52	$218.50	$218.50
Purchase #7	$181.90	11.537%	$202.8858	$202.89	$202.90	$202.90
7 purchase totals =	$938.09		$1,035.9570	$1,035.97	$1,035.95	$1,036.00