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	$90.75	12.833%	$102.3959	$102.40	$102.40	$102.40
Purchase #2	$155.46	4.611%	$162.6283	$162.63	$162.65	$162.60
Purchase #3	$107.58	4.389%	$112.3017	$112.30	$112.30	$112.30
Purchase #4	$41.46	9.174%	$45.2635	$45.26	$45.25	$45.30
Purchase #5	$137.64	9.268%	$150.3965	$150.40	$150.40	$150.40
Purchase #6	$201.57	12.866%	$227.504	$227.50	$227.50	$227.50
Purchase #7	$237.65	7.846%	$256.296	$256.30	$256.30	$256.30
7 purchase totals =	$972.11		$1,056.7859	$1,056.79	$1,056.80	$1,056.80