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	$28.86	13.749%	$32.828	$32.83	$32.85	$32.80
Purchase #2	$40.34	4.233%	$42.0476	$42.05	$42.05	$42.00
Purchase #3	$49.38	11.770%	$55.192	$55.19	$55.20	$55.20
Purchase #4	$34.53	13.666%	$39.2489	$39.25	$39.25	$39.20
Purchase #5	$97.82	13.502%	$111.0277	$111.03	$111.05	$111.00
Purchase #6	$61.95	8.847%	$67.4307	$67.43	$67.45	$67.40
Purchase #7	$35.42	10.134%	$39.0095	$39.01	$39.00	$39.00
7 purchase totals =	$348.30		$386.7844	$386.79	$386.85	$386.60