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	$242.44	5.836%	$256.5888	$256.59	$256.60	$256.60
Purchase #2	$28.82	9.430%	$31.5377	$31.54	$31.55	$31.50
Purchase #3	$162.63	8.481%	$176.4227	$176.42	$176.40	$176.40
Purchase #4	$73.53	8.632%	$79.8771	$79.88	$79.90	$79.90
Purchase #5	$85.71	10.469%	$94.683	$94.68	$94.70	$94.70
Purchase #6	$224.58	6.632%	$239.4741	$239.47	$239.45	$239.50
Purchase #7	$167.50	9.443%	$183.317	$183.32	$183.30	$183.30
7 purchase totals =	$985.21		$1,061.9004	$1,061.90	$1,061.90	$1,061.90