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	$152.77	3.768%	$158.5264	$158.53	$158.55	$158.50
Purchase #2	$11.71	4.503%	$12.2373	$12.24	$12.25	$12.20
Purchase #3	$113.39	13.333%	$128.5083	$128.51	$128.50	$128.50
Purchase #4	$225.39	4.412%	$235.3342	$235.33	$235.35	$235.30
Purchase #5	$228.98	5.239%	$240.9763	$240.98	$241.00	$241.00
Purchase #6	$94.60	4.691%	$99.0377	$99.04	$99.05	$99.00
Purchase #7	$131.93	5.873%	$139.6782	$139.68	$139.70	$139.70
7 purchase totals =	$958.77		$1,014.2984	$1,014.31	$1,014.40	$1,014.20