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	$235.26	11.824%	$263.0771	$263.08	$263.10	$263.10
Purchase #2	$133.74	6.364%	$142.2512	$142.25	$142.25	$142.30
Purchase #3	$151.82	12.688%	$171.0829	$171.08	$171.10	$171.10
Purchase #4	$86.50	4.687%	$90.5543	$90.55	$90.55	$90.60
Purchase #5	$31.59	7.649%	$34.0063	$34.01	$34.00	$34.00
Purchase #6	$123.83	13.121%	$140.0777	$140.08	$140.10	$140.10
Purchase #7	$228.96	5.678%	$241.9603	$241.96	$241.95	$242.00
7 purchase totals =	$991.70		$1,083.0098	$1,083.01	$1,083.05	$1,083.20