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	$51.84	12.737%	$58.4429	$58.44	$58.45	$58.40
Purchase #2	$5.46	9.119%	$5.9579	$5.96	$5.95	$6.00
Purchase #3	$106.84	4.379%	$111.5185	$111.52	$111.50	$111.50
Purchase #4	$64.87	3.799%	$67.3344	$67.33	$67.35	$67.30
Purchase #5	$243.81	9.274%	$266.4209	$266.42	$266.40	$266.40
Purchase #6	$31.47	3.487%	$32.5674	$32.57	$32.55	$32.60
Purchase #7	$213.28	13.789%	$242.6892	$242.69	$242.70	$242.70
7 purchase totals =	$717.57		$784.9312	$784.93	$784.90	$784.90