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	$88.67	11.733%	$99.0737	$99.07	$99.05	$99.10
Purchase #2	$60.26	4.426%	$62.9271	$62.93	$62.95	$62.90
Purchase #3	$242.98	7.238%	$260.5669	$260.57	$260.55	$260.60
Purchase #4	$137.57	3.456%	$142.3244	$142.32	$142.30	$142.30
Purchase #5	$127.64	3.401%	$131.981	$131.98	$132.00	$132.00
Purchase #6	$152.91	10.179%	$168.4747	$168.47	$168.45	$168.50
Purchase #7	$89.96	7.484%	$96.6926	$96.69	$96.70	$96.70
7 purchase totals =	$899.99		$962.0404	$962.03	$962.00	$962.10