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	$32.47	3.547%	$33.6217	$33.62	$33.60	$33.60
Purchase #2	$28.32	4.751%	$29.6655	$29.67	$29.65	$29.70
Purchase #3	$25.58	13.200%	$28.9566	$28.96	$28.95	$29.00
Purchase #4	$217.72	10.854%	$241.3513	$241.35	$241.35	$241.40
Purchase #5	$178.96	11.795%	$200.0683	$200.07	$200.05	$200.10
Purchase #6	$198.40	12.846%	$223.8865	$223.89	$223.90	$223.90
Purchase #7	$8.27	12.858%	$9.3334	$9.33	$9.35	$9.30
7 purchase totals =	$689.72		$766.8833	$766.89	$766.85	$767.00