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	$110.80	3.497%	$114.6747	$114.67	$114.65	$114.70
Purchase #2	$41.90	8.426%	$45.4305	$45.43	$45.45	$45.40
Purchase #3	$114.57	13.665%	$130.226	$130.23	$130.25	$130.20
Purchase #4	$182.64	4.486%	$190.8332	$190.83	$190.85	$190.80
Purchase #5	$220.45	9.554%	$241.5118	$241.51	$241.50	$241.50
Purchase #6	$34.61	3.555%	$35.8404	$35.84	$35.85	$35.80
Purchase #7	$147.52	13.581%	$167.5547	$167.55	$167.55	$167.60
7 purchase totals =	$852.49		$926.0713	$926.06	$926.10	$926.00