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	$176.67	11.217%	$196.4871	$196.49	$196.50	$196.50
Purchase #2	$145.75	10.185%	$160.5946	$160.59	$160.60	$160.60
Purchase #3	$247.45	7.147%	$265.1353	$265.14	$265.15	$265.10
Purchase #4	$67.42	7.573%	$72.5257	$72.53	$72.55	$72.50
Purchase #5	$195.52	7.417%	$210.0217	$210.02	$210.00	$210.00
Purchase #6	$236.78	9.521%	$259.3238	$259.32	$259.30	$259.30
Purchase #7	$224.94	7.454%	$241.707	$241.71	$241.70	$241.70
7 purchase totals =	$1,294.53		$1,405.7952	$1,405.80	$1,405.80	$1,405.70