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	$187.94	6.441%	$200.0452	$200.05	$200.05	$200.00
Purchase #2	$121.75	8.397%	$131.9733	$131.97	$131.95	$132.00
Purchase #3	$18.59	13.615%	$21.121	$21.12	$21.10	$21.10
Purchase #4	$132.29	3.207%	$136.5325	$136.53	$136.55	$136.50
Purchase #5	$152.86	12.202%	$171.512	$171.51	$171.50	$171.50
Purchase #6	$80.79	11.742%	$90.2764	$90.28	$90.30	$90.30
Purchase #7	$115.70	13.414%	$131.22	$131.22	$131.20	$131.20
7 purchase totals =	$809.92		$882.6804	$882.68	$882.65	$882.60