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	$161.64	7.816%	$174.2738	$174.27	$174.25	$174.30
Purchase #2	$139.95	13.231%	$158.4668	$158.47	$158.45	$158.50
Purchase #3	$50.34	11.315%	$56.036	$56.04	$56.05	$56.00
Purchase #4	$31.38	9.535%	$34.3721	$34.37	$34.35	$34.40
Purchase #5	$98.57	7.294%	$105.7597	$105.76	$105.75	$105.80
Purchase #6	$236.39	12.105%	$265.005	$265.01	$265.00	$265.00
Purchase #7	$43.65	12.345%	$49.0386	$49.04	$49.05	$49.00
7 purchase totals =	$761.92		$842.9520	$842.96	$842.90	$843.00