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	$128.61	7.247%	$137.9304	$137.93	$137.95	$137.90
Purchase #2	$83.67	7.269%	$89.752	$89.75	$89.75	$89.80
Purchase #3	$37.50	3.797%	$38.9239	$38.92	$38.90	$38.90
Purchase #4	$51.30	8.179%	$55.4958	$55.50	$55.50	$55.50
Purchase #5	$186.44	13.554%	$211.7101	$211.71	$211.70	$211.70
Purchase #6	$90.93	8.792%	$98.9246	$98.92	$98.90	$98.90
Purchase #7	$118.47	11.440%	$132.023	$132.02	$132.00	$132.00
7 purchase totals =	$696.92		$764.7598	$764.75	$764.70	$764.70