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	$84.97	13.269%	$96.2447	$96.24	$96.25	$96.20
Purchase #2	$186.50	5.263%	$196.3155	$196.32	$196.30	$196.30
Purchase #3	$228.99	3.718%	$237.5038	$237.50	$237.50	$237.50
Purchase #4	$103.46	10.504%	$114.3274	$114.33	$114.35	$114.30
Purchase #5	$203.78	9.341%	$222.8151	$222.82	$222.80	$222.80
Purchase #6	$98.52	13.688%	$112.0054	$112.01	$112.00	$112.00
Purchase #7	$66.72	8.619%	$72.4706	$72.47	$72.45	$72.50
7 purchase totals =	$972.94		$1,051.6825	$1,051.69	$1,051.65	$1,051.60