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	$18.91	4.871%	$19.8311	$19.83	$19.85	$19.80
Purchase #2	$40.68	5.861%	$43.0643	$43.06	$43.05	$43.10
Purchase #3	$95.61	3.112%	$98.5854	$98.59	$98.60	$98.60
Purchase #4	$233.48	12.235%	$262.0463	$262.05	$262.05	$262.00
Purchase #5	$115.54	6.665%	$123.2407	$123.24	$123.25	$123.20
Purchase #6	$166.96	4.424%	$174.3463	$174.35	$174.35	$174.30
Purchase #7	$181.91	13.112%	$205.762	$205.76	$205.75	$205.80
7 purchase totals =	$853.09		$926.8761	$926.88	$926.90	$926.80