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	$177.92	12.725%	$200.5603	$200.56	$200.55	$200.60
Purchase #2	$38.65	7.460%	$41.5333	$41.53	$41.55	$41.50
Purchase #3	$160.64	4.760%	$168.2865	$168.29	$168.30	$168.30
Purchase #4	$119.58	6.114%	$126.8911	$126.89	$126.90	$126.90
Purchase #5	$63.64	11.178%	$70.7537	$70.75	$70.75	$70.80
Purchase #6	$57.75	3.665%	$59.8665	$59.87	$59.85	$59.90
Purchase #7	$80.40	11.761%	$89.8558	$89.86	$89.85	$89.90
7 purchase totals =	$698.58		$757.7472	$757.75	$757.75	$757.90