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	$24.93	5.402%	$26.2767	$26.28	$26.30	$26.30
Purchase #2	$35.55	8.597%	$38.6062	$38.61	$38.60	$38.60
Purchase #3	$82.62	10.800%	$91.543	$91.54	$91.55	$91.50
Purchase #4	$210.90	4.567%	$220.5318	$220.53	$220.55	$220.50
Purchase #5	$246.39	10.429%	$272.086	$272.09	$272.10	$272.10
Purchase #6	$101.64	9.265%	$111.0569	$111.06	$111.05	$111.10
Purchase #7	$26.51	3.820%	$27.5227	$27.52	$27.50	$27.50
7 purchase totals =	$728.54		$787.6233	$787.63	$787.65	$787.60