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	$32.72	9.527%	$35.8372	$35.84	$35.85	$35.80
Purchase #2	$30.29	12.288%	$34.012	$34.01	$34.00	$34.00
Purchase #3	$31.28	12.283%	$35.1221	$35.12	$35.10	$35.10
Purchase #4	$124.32	6.375%	$132.2454	$132.25	$132.25	$132.20
Purchase #5	$202.40	10.472%	$223.5953	$223.60	$223.60	$223.60
Purchase #6	$155.75	4.309%	$162.4613	$162.46	$162.45	$162.50
Purchase #7	$147.39	13.571%	$167.3923	$167.39	$167.40	$167.40
7 purchase totals =	$724.15		$790.6656	$790.67	$790.65	$790.60